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 $84.83   12.294%   $95.259   $95.26   $95.25   $95.30  
  Purchase #2 $104.49   3.324%   $107.9632   $107.96   $107.95   $108.00  
  Purchase #3 $9.67   3.356%   $9.9945   $9.99   $10.00   $10.00  
  Purchase #4 $201.41   12.602%   $226.7917   $226.79   $226.80   $226.80  
  Purchase #5 $98.36   3.420%   $101.7239   $101.72   $101.70   $101.70  
  Purchase #6 $184.85   12.649%   $208.2317   $208.23   $208.25   $208.20  
  Purchase #7 $170.41   13.105%   $192.7422   $192.74   $192.75   $192.70  
  7 purchase totals = $854.02       $942.7062   $942.69   $942.70   $942.70