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 $211.57   10.723%   $234.2567   $234.26   $234.25   $234.30  
  Purchase #2 $147.70   10.355%   $162.9943   $162.99   $163.00   $163.00  
  Purchase #3 $161.34   4.460%   $168.5358   $168.54   $168.55   $168.50  
  Purchase #4 $57.84   5.521%   $61.0333   $61.03   $61.05   $61.00  
  Purchase #5 $108.61   10.371%   $119.8739   $119.87   $119.85   $119.90  
  Purchase #6 $246.94   6.497%   $262.9837   $262.98   $263.00   $263.00  
  Purchase #7 $240.83   3.847%   $250.0947   $250.09   $250.10   $250.10  
  7 purchase totals = $1,174.83       $1,259.7724   $1,259.76   $1,259.80   $1,259.80