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 $91.80   3.526%   $95.0369   $95.04   $95.05   $95.00  
  Purchase #2 $36.69   13.670%   $41.7055   $41.71   $41.70   $41.70  
  Purchase #3 $89.68   5.291%   $94.425   $94.43   $94.45   $94.40  
  Purchase #4 $181.48   7.603%   $195.2779   $195.28   $195.30   $195.30  
  Purchase #5 $123.28   11.204%   $137.0923   $137.09   $137.10   $137.10  
  Purchase #6 $167.78   11.522%   $187.1116   $187.11   $187.10   $187.10  
  Purchase #7 $138.45   3.730%   $143.6142   $143.61   $143.60   $143.60  
  7 purchase totals = $829.16       $894.2634   $894.27   $894.30   $894.20