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 $22.43   7.521%   $24.117   $24.12   $24.10   $24.10  
  Purchase #2 $85.42   10.566%   $94.4455   $94.45   $94.45   $94.40  
  Purchase #3 $148.58   12.392%   $166.992   $166.99   $167.00   $167.00  
  Purchase #4 $54.69   9.693%   $59.9911   $59.99   $60.00   $60.00  
  Purchase #5 $247.94   7.335%   $266.1264   $266.13   $266.15   $266.10  
  Purchase #6 $92.69   10.851%   $102.7478   $102.75   $102.75   $102.70  
  Purchase #7 $42.92   7.487%   $46.1334   $46.13   $46.15   $46.10  
  7 purchase totals = $694.67       $760.5532   $760.56   $760.60   $760.40