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 $68.95   7.786%   $74.3184   $74.32   $74.30   $74.30  
  Purchase #2 $97.43   6.575%   $103.836   $103.84   $103.85   $103.80  
  Purchase #3 $80.40   13.781%   $91.4799   $91.48   $91.50   $91.50  
  Purchase #4 $64.50   11.805%   $72.1142   $72.11   $72.10   $72.10  
  Purchase #5 $67.58   9.362%   $73.9068   $73.91   $73.90   $73.90  
  Purchase #6 $120.27   13.605%   $136.6327   $136.63   $136.65   $136.60  
  Purchase #7 $200.94   6.198%   $213.3943   $213.39   $213.40   $213.40  
  7 purchase totals = $700.07       $765.6823   $765.68   $765.70   $765.60