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 $77.34   12.811%   $87.248   $87.25   $87.25   $87.20  
  Purchase #2 $114.76   9.626%   $125.8068   $125.81   $125.80   $125.80  
  Purchase #3 $20.90   6.845%   $22.3306   $22.33   $22.35   $22.30  
  Purchase #4 $111.86   6.676%   $119.3278   $119.33   $119.35   $119.30  
  Purchase #5 $46.81   6.267%   $49.7436   $49.74   $49.75   $49.70  
  Purchase #6 $224.51   4.814%   $235.3179   $235.32   $235.30   $235.30  
  Purchase #7 $100.33   7.576%   $107.931   $107.93   $107.95   $107.90  
  7 purchase totals = $696.51       $747.7057   $747.71   $747.75   $747.50