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 $76.68   7.425%   $82.3735   $82.37   $82.35   $82.40  
  Purchase #2 $236.35   5.138%   $248.4937   $248.49   $248.50   $248.50  
  Purchase #3 $33.55   7.617%   $36.1055   $36.11   $36.10   $36.10  
  Purchase #4 $145.54   8.747%   $158.2704   $158.27   $158.25   $158.30  
  Purchase #5 $142.55   5.121%   $149.85   $149.85   $149.85   $149.90  
  Purchase #6 $29.32   5.802%   $31.0211   $31.02   $31.00   $31.00  
  Purchase #7 $231.36   10.645%   $255.9883   $255.99   $256.00   $256.00  
  7 purchase totals = $895.35       $962.1025   $962.10   $962.05   $962.20