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 $61.63   13.523%   $69.9642   $69.96   $69.95   $70.00  
  Purchase #2 $180.91   6.301%   $192.3091   $192.31   $192.30   $192.30  
  Purchase #3 $92.35   12.664%   $104.0452   $104.05   $104.05   $104.00  
  Purchase #4 $13.74   12.187%   $15.4145   $15.41   $15.40   $15.40  
  Purchase #5 $180.63   12.105%   $202.4953   $202.50   $202.50   $202.50  
  Purchase #6 $189.97   8.793%   $206.6741   $206.67   $206.65   $206.70  
  Purchase #7 $211.40   10.735%   $234.0938   $234.09   $234.10   $234.10  
  7 purchase totals = $930.63       $1,024.9962   $1,024.99   $1,024.95   $1,025.00