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 $212.65   4.728%   $222.7041   $222.70   $222.70   $222.70  
  Purchase #2 $73.54   3.489%   $76.1058   $76.11   $76.10   $76.10  
  Purchase #3 $88.32   6.673%   $94.2136   $94.21   $94.20   $94.20  
  Purchase #4 $249.50   11.838%   $279.0358   $279.04   $279.05   $279.00  
  Purchase #5 $119.51   12.260%   $134.1619   $134.16   $134.15   $134.20  
  Purchase #6 $216.88   6.679%   $231.3654   $231.37   $231.35   $231.40  
  Purchase #7 $209.81   7.819%   $226.215   $226.22   $226.20   $226.20  
  7 purchase totals = $1,170.21       $1,263.8016   $1,263.81   $1,263.75   $1,263.80