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 $41.27   13.824%   $46.9752   $46.98   $47.00   $47.00  
  Purchase #2 $119.41   10.397%   $131.8251   $131.83   $131.85   $131.80  
  Purchase #3 $14.70   9.426%   $16.0856   $16.09   $16.10   $16.10  
  Purchase #4 $122.96   6.270%   $130.6696   $130.67   $130.65   $130.70  
  Purchase #5 $138.74   5.660%   $146.5927   $146.59   $146.60   $146.60  
  Purchase #6 $75.55   11.549%   $84.2753   $84.28   $84.30   $84.30  
  Purchase #7 $152.95   10.763%   $169.412   $169.41   $169.40   $169.40  
  7 purchase totals = $665.58       $725.8355   $725.85   $725.90   $725.90