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 $84.51   11.266%   $94.0309   $94.03   $94.05   $94.00  
  Purchase #2 $235.37   3.499%   $243.6056   $243.61   $243.60   $243.60  
  Purchase #3 $97.65   11.291%   $108.6757   $108.68   $108.70   $108.70  
  Purchase #4 $57.28   3.301%   $59.1708   $59.17   $59.15   $59.20  
  Purchase #5 $93.26   9.507%   $102.1262   $102.13   $102.15   $102.10  
  Purchase #6 $93.99   9.423%   $102.8467   $102.85   $102.85   $102.80  
  Purchase #7 $60.38   5.792%   $63.8772   $63.88   $63.90   $63.90  
  7 purchase totals = $722.44       $774.3331   $774.35   $774.40   $774.30