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 $184.78   5.644%   $195.209   $195.21   $195.20   $195.20  
  Purchase #2 $53.36   3.849%   $55.4138   $55.41   $55.40   $55.40  
  Purchase #3 $164.30   13.783%   $186.9455   $186.95   $186.95   $186.90  
  Purchase #4 $41.96   9.554%   $45.9689   $45.97   $45.95   $46.00  
  Purchase #5 $124.26   5.141%   $130.6482   $130.65   $130.65   $130.60  
  Purchase #6 $24.70   13.462%   $28.0251   $28.03   $28.05   $28.00  
  Purchase #7 $147.37   11.152%   $163.8047   $163.80   $163.80   $163.80  
  7 purchase totals = $740.73       $806.0152   $806.02   $806.00   $805.90