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 $91.29   4.802%   $95.6737   $95.67   $95.65   $95.70  
  Purchase #2 $208.56   8.473%   $226.2313   $226.23   $226.25   $226.20  
  Purchase #3 $66.50   4.486%   $69.4832   $69.48   $69.50   $69.50  
  Purchase #4 $61.77   6.857%   $66.0056   $66.01   $66.00   $66.00  
  Purchase #5 $232.47   4.277%   $242.4127   $242.41   $242.40   $242.40  
  Purchase #6 $157.75   7.331%   $169.3147   $169.31   $169.30   $169.30  
  Purchase #7 $17.63   3.827%   $18.3047   $18.30   $18.30   $18.30  
  7 purchase totals = $835.97       $887.4259   $887.41   $887.40   $887.40