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 $223.72   7.757%   $241.074   $241.07   $241.05   $241.10  
  Purchase #2 $60.59   7.549%   $65.1639   $65.16   $65.15   $65.20  
  Purchase #3 $216.81   7.197%   $232.4138   $232.41   $232.40   $232.40  
  Purchase #4 $25.29   8.228%   $27.3709   $27.37   $27.35   $27.40  
  Purchase #5 $161.34   9.458%   $176.5995   $176.60   $176.60   $176.60  
  Purchase #6 $24.45   6.782%   $26.1082   $26.11   $26.10   $26.10  
  Purchase #7 $191.62   4.325%   $199.9076   $199.91   $199.90   $199.90  
  7 purchase totals = $903.82       $968.6379   $968.63   $968.55   $968.70