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 $126.65   6.510%   $134.8949   $134.89   $134.90   $134.90  
  Purchase #2 $121.26   8.313%   $131.3403   $131.34   $131.35   $131.30  
  Purchase #3 $62.50   8.779%   $67.9869   $67.99   $68.00   $68.00  
  Purchase #4 $36.94   6.181%   $39.2233   $39.22   $39.20   $39.20  
  Purchase #5 $113.62   5.853%   $120.2702   $120.27   $120.25   $120.30  
  Purchase #6 $218.92   8.114%   $236.6832   $236.68   $236.70   $236.70  
  Purchase #7 $175.42   11.733%   $196.002   $196.00   $196.00   $196.00  
  7 purchase totals = $855.31       $926.4008   $926.39   $926.40   $926.40