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 $55.26   13.871%   $62.9251   $62.93   $62.95   $62.90  
  Purchase #2 $23.71   6.786%   $25.319   $25.32   $25.30   $25.30  
  Purchase #3 $149.90   10.867%   $166.1896   $166.19   $166.20   $166.20  
  Purchase #4 $69.95   7.390%   $75.1193   $75.12   $75.10   $75.10  
  Purchase #5 $156.93   3.475%   $162.3833   $162.38   $162.40   $162.40  
  Purchase #6 $150.88   11.847%   $168.7548   $168.75   $168.75   $168.80  
  Purchase #7 $67.55   5.624%   $71.349   $71.35   $71.35   $71.30  
  7 purchase totals = $674.18       $732.0401   $732.04   $732.05   $732.00