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 $24.63   5.657%   $26.0233   $26.02   $26.00   $26.00  
  Purchase #2 $244.83   11.325%   $272.557   $272.56   $272.55   $272.60  
  Purchase #3 $202.41   11.721%   $226.1345   $226.13   $226.15   $226.10  
  Purchase #4 $5.78   5.713%   $6.1102   $6.11   $6.10   $6.10  
  Purchase #5 $104.90   3.790%   $108.8757   $108.88   $108.90   $108.90  
  Purchase #6 $92.37   6.518%   $98.3907   $98.39   $98.40   $98.40  
  Purchase #7 $227.69   6.757%   $243.075   $243.08   $243.10   $243.10  
  7 purchase totals = $902.61       $981.1664   $981.17   $981.20   $981.20