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 $84.62   12.380%   $95.096   $95.10   $95.10   $95.10  
  Purchase #2 $62.74   7.843%   $67.6607   $67.66   $67.65   $67.70  
  Purchase #3 $73.31   5.397%   $77.2665   $77.27   $77.25   $77.30  
  Purchase #4 $160.28   12.603%   $180.4801   $180.48   $180.50   $180.50  
  Purchase #5 $68.44   11.763%   $76.4906   $76.49   $76.50   $76.50  
  Purchase #6 $184.52   6.458%   $196.4363   $196.44   $196.45   $196.40  
  Purchase #7 $242.27   10.804%   $268.4449   $268.44   $268.45   $268.40  
  7 purchase totals = $876.18       $961.8751   $961.88   $961.90   $961.90