Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $208.66   9.843%   $229.1984   $229.20   $229.20   $229.20  
  Purchase #2 $179.37   13.871%   $204.2504   $204.25   $204.25   $204.30  
  Purchase #3 $246.58   4.257%   $257.0769   $257.08   $257.10   $257.10  
  Purchase #4 $236.68   11.506%   $263.9124   $263.91   $263.90   $263.90  
  Purchase #5 $118.67   5.496%   $125.1921   $125.19   $125.20   $125.20  
  Purchase #6 $231.36   13.569%   $262.7532   $262.75   $262.75   $262.80  
  Purchase #7 $129.98   7.109%   $139.2203   $139.22   $139.20   $139.20  
  7 purchase totals = $1,351.30       $1,481.6037   $1,481.60   $1,481.60   $1,481.70