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 $71.29   3.722%   $73.9434   $73.94   $73.95   $73.90  
  Purchase #2 $244.63   9.528%   $267.9383   $267.94   $267.95   $267.90  
  Purchase #3 $86.38   5.817%   $91.4047   $91.40   $91.40   $91.40  
  Purchase #4 $191.50   8.503%   $207.7832   $207.78   $207.80   $207.80  
  Purchase #5 $134.74   11.319%   $149.9912   $149.99   $150.00   $150.00  
  Purchase #6 $178.25   5.210%   $187.5368   $187.54   $187.55   $187.50  
  Purchase #7 $67.44   11.167%   $74.971   $74.97   $74.95   $75.00  
  7 purchase totals = $974.23       $1,053.5686   $1,053.56   $1,053.60   $1,053.50