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 $142.75   6.533%   $152.0759   $152.08   $152.10   $152.10  
  Purchase #2 $59.84   4.244%   $62.3796   $62.38   $62.40   $62.40  
  Purchase #3 $116.94   11.104%   $129.925   $129.93   $129.95   $129.90  
  Purchase #4 $248.52   9.468%   $272.0499   $272.05   $272.05   $272.00  
  Purchase #5 $156.25   3.477%   $161.6828   $161.68   $161.70   $161.70  
  Purchase #6 $230.82   7.434%   $247.9792   $247.98   $248.00   $248.00  
  Purchase #7 $138.93   11.105%   $154.3582   $154.36   $154.35   $154.40  
  7 purchase totals = $1,094.05       $1,180.4506   $1,180.46   $1,180.55   $1,180.50