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 $87.39   10.313%   $96.4025   $96.40   $96.40   $96.40  
  Purchase #2 $112.32   12.369%   $126.2129   $126.21   $126.20   $126.20  
  Purchase #3 $26.96   9.121%   $29.419   $29.42   $29.40   $29.40  
  Purchase #4 $86.95   6.398%   $92.5131   $92.51   $92.50   $92.50  
  Purchase #5 $204.66   5.424%   $215.7608   $215.76   $215.75   $215.80  
  Purchase #6 $123.31   7.599%   $132.6803   $132.68   $132.70   $132.70  
  Purchase #7 $72.67   3.210%   $75.0027   $75.00   $75.00   $75.00  
  7 purchase totals = $714.26       $767.9913   $767.98   $767.95   $768.00