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 $43.66   11.624%   $48.735   $48.74   $48.75   $48.70  
  Purchase #2 $19.26   13.417%   $21.8441   $21.84   $21.85   $21.80  
  Purchase #3 $62.69   8.466%   $67.9973   $68.00   $68.00   $68.00  
  Purchase #4 $242.35   5.616%   $255.9604   $255.96   $255.95   $256.00  
  Purchase #5 $242.29   8.765%   $263.5267   $263.53   $263.55   $263.50  
  Purchase #6 $41.57   13.497%   $47.1807   $47.18   $47.20   $47.20  
  Purchase #7 $44.89   8.858%   $48.8664   $48.87   $48.85   $48.90  
  7 purchase totals = $696.71       $754.1106   $754.12   $754.15   $754.10