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 $224.63   5.342%   $236.6297   $236.63   $236.65   $236.60  
  Purchase #2 $221.79   7.137%   $237.6192   $237.62   $237.60   $237.60  
  Purchase #3 $155.46   9.323%   $169.9535   $169.95   $169.95   $170.00  
  Purchase #4 $34.60   10.464%   $38.2205   $38.22   $38.20   $38.20  
  Purchase #5 $59.86   4.555%   $62.5866   $62.59   $62.60   $62.60  
  Purchase #6 $237.56   11.219%   $264.2119   $264.21   $264.20   $264.20  
  Purchase #7 $242.79   6.759%   $259.2002   $259.20   $259.20   $259.20  
  7 purchase totals = $1,176.69       $1,268.4216   $1,268.42   $1,268.40   $1,268.40