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 $62.83   12.394%   $70.6172   $70.62   $70.60   $70.60  
  Purchase #2 $185.51   8.777%   $201.7922   $201.79   $201.80   $201.80  
  Purchase #3 $25.81   8.211%   $27.9293   $27.93   $27.95   $27.90  
  Purchase #4 $157.47   6.648%   $167.9386   $167.94   $167.95   $167.90  
  Purchase #5 $206.45   13.515%   $234.3517   $234.35   $234.35   $234.40  
  Purchase #6 $116.25   8.290%   $125.8871   $125.89   $125.90   $125.90  
  Purchase #7 $174.54   11.592%   $194.7727   $194.77   $194.75   $194.80  
  7 purchase totals = $928.86       $1,023.2888   $1,023.29   $1,023.30   $1,023.30