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 $84.65   10.736%   $93.738   $93.74   $93.75   $93.70  
  Purchase #2 $56.36   4.598%   $58.9514   $58.95   $58.95   $59.00  
  Purchase #3 $148.86   10.674%   $164.7493   $164.75   $164.75   $164.70  
  Purchase #4 $224.50   6.294%   $238.63   $238.63   $238.65   $238.60  
  Purchase #5 $32.40   11.509%   $36.1289   $36.13   $36.15   $36.10  
  Purchase #6 $14.91   4.785%   $15.6234   $15.62   $15.60   $15.60  
  Purchase #7 $110.31   6.789%   $117.7989   $117.80   $117.80   $117.80  
  7 purchase totals = $671.99       $725.6199   $725.62   $725.65   $725.50