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 $51.51   10.523%   $56.9304   $56.93   $56.95   $56.90  
  Purchase #2 $189.50   10.127%   $208.6907   $208.69   $208.70   $208.70  
  Purchase #3 $80.98   10.141%   $89.1922   $89.19   $89.20   $89.20  
  Purchase #4 $90.60   13.344%   $102.6897   $102.69   $102.70   $102.70  
  Purchase #5 $197.51   3.627%   $204.6737   $204.67   $204.65   $204.70  
  Purchase #6 $57.75   7.276%   $61.9519   $61.95   $61.95   $62.00  
  Purchase #7 $102.80   4.872%   $107.8084   $107.81   $107.80   $107.80  
  7 purchase totals = $770.65       $831.9370   $831.93   $831.95   $832.00