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 $214.50   10.126%   $236.2203   $236.22   $236.20   $236.20  
  Purchase #2 $204.88   13.542%   $232.6248   $232.62   $232.60   $232.60  
  Purchase #3 $247.87   6.677%   $264.4203   $264.42   $264.40   $264.40  
  Purchase #4 $71.67   13.310%   $81.2093   $81.21   $81.20   $81.20  
  Purchase #5 $109.93   5.145%   $115.5859   $115.59   $115.60   $115.60  
  Purchase #6 $241.78   3.859%   $251.1103   $251.11   $251.10   $251.10  
  Purchase #7 $78.87   5.356%   $83.0943   $83.09   $83.10   $83.10  
  7 purchase totals = $1,169.50       $1,264.2652   $1,264.26   $1,264.20   $1,264.20