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 $41.28   8.394%   $44.745   $44.75   $44.75   $44.70  
  Purchase #2 $98.86   8.526%   $107.2888   $107.29   $107.30   $107.30  
  Purchase #3 $151.84   8.553%   $164.8269   $164.83   $164.85   $164.80  
  Purchase #4 $197.31   4.556%   $206.2994   $206.30   $206.30   $206.30  
  Purchase #5 $150.60   11.774%   $168.3316   $168.33   $168.35   $168.30  
  Purchase #6 $58.82   4.267%   $61.3298   $61.33   $61.35   $61.30  
  Purchase #7 $9.77   5.208%   $10.2788   $10.28   $10.30   $10.30  
  7 purchase totals = $708.48       $763.1003   $763.11   $763.20   $763.00