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 $62.65   7.624%   $67.4264   $67.43   $67.45   $67.40  
  Purchase #2 $179.75   8.793%   $195.5554   $195.56   $195.55   $195.60  
  Purchase #3 $208.82   11.105%   $232.0095   $232.01   $232.00   $232.00  
  Purchase #4 $236.26   11.341%   $263.0542   $263.05   $263.05   $263.10  
  Purchase #5 $157.39   11.795%   $175.9542   $175.95   $175.95   $176.00  
  Purchase #6 $101.57   12.124%   $113.8843   $113.88   $113.90   $113.90  
  Purchase #7 $140.78   8.182%   $152.2986   $152.30   $152.30   $152.30  
  7 purchase totals = $1,087.22       $1,200.1826   $1,200.18   $1,200.20   $1,200.30