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 $87.46   7.552%   $94.065   $94.07   $94.05   $94.10  
  Purchase #2 $128.72   7.673%   $138.5967   $138.60   $138.60   $138.60  
  Purchase #3 $162.69   9.491%   $178.1309   $178.13   $178.15   $178.10  
  Purchase #4 $44.94   3.609%   $46.5619   $46.56   $46.55   $46.60  
  Purchase #5 $104.34   3.508%   $108.0002   $108.00   $108.00   $108.00  
  Purchase #6 $166.52   5.810%   $176.1948   $176.19   $176.20   $176.20  
  Purchase #7 $232.49   3.397%   $240.3877   $240.39   $240.40   $240.40  
  7 purchase totals = $927.16       $981.9372   $981.94   $981.95   $982.00