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 $63.68   11.505%   $71.0064   $71.01   $71.00   $71.00  
  Purchase #2 $177.26   10.387%   $195.672   $195.67   $195.65   $195.70  
  Purchase #3 $155.92   13.132%   $176.3954   $176.40   $176.40   $176.40  
  Purchase #4 $19.99   7.769%   $21.543   $21.54   $21.55   $21.50  
  Purchase #5 $166.97   13.568%   $189.6245   $189.62   $189.60   $189.60  
  Purchase #6 $180.92   8.267%   $195.8767   $195.88   $195.90   $195.90  
  Purchase #7 $95.78   7.860%   $103.3083   $103.31   $103.30   $103.30  
  7 purchase totals = $860.52       $953.4263   $953.43   $953.40   $953.40