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 $114.61   10.657%   $126.824   $126.82   $126.80   $126.80  
  Purchase #2 $35.34   5.216%   $37.1833   $37.18   $37.20   $37.20  
  Purchase #3 $128.92   9.192%   $140.7703   $140.77   $140.75   $140.80  
  Purchase #4 $194.69   8.389%   $211.0225   $211.02   $211.00   $211.00  
  Purchase #5 $24.97   4.631%   $26.1264   $26.13   $26.15   $26.10  
  Purchase #6 $135.37   5.246%   $142.4715   $142.47   $142.45   $142.50  
  Purchase #7 $44.53   8.138%   $48.1539   $48.15   $48.15   $48.20  
  7 purchase totals = $678.43       $732.5519   $732.54   $732.50   $732.60