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 $45.33   3.437%   $46.888   $46.89   $46.90   $46.90  
  Purchase #2 $135.27   4.871%   $141.859   $141.86   $141.85   $141.90  
  Purchase #3 $44.62   7.405%   $47.9241   $47.92   $47.90   $47.90  
  Purchase #4 $213.57   10.407%   $235.7962   $235.80   $235.80   $235.80  
  Purchase #5 $169.56   11.843%   $189.641   $189.64   $189.65   $189.60  
  Purchase #6 $62.52   8.786%   $68.013   $68.01   $68.00   $68.00  
  Purchase #7 $155.90   10.783%   $172.7107   $172.71   $172.70   $172.70  
  7 purchase totals = $826.77       $902.8320   $902.83   $902.80   $902.80