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 $22.60   7.761%   $24.354   $24.35   $24.35   $24.40  
  Purchase #2 $212.63   12.687%   $239.6064   $239.61   $239.60   $239.60  
  Purchase #3 $14.52   3.314%   $15.0012   $15.00   $15.00   $15.00  
  Purchase #4 $21.81   11.250%   $24.2636   $24.26   $24.25   $24.30  
  Purchase #5 $194.87   7.394%   $209.2787   $209.28   $209.30   $209.30  
  Purchase #6 $158.25   7.231%   $169.6931   $169.69   $169.70   $169.70  
  Purchase #7 $70.31   13.484%   $79.7906   $79.79   $79.80   $79.80  
  7 purchase totals = $694.99       $761.9876   $761.98   $762.00   $762.10