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 $213.85   10.670%   $236.6678   $236.67   $236.65   $236.70  
  Purchase #2 $34.29   5.833%   $36.2901   $36.29   $36.30   $36.30  
  Purchase #3 $236.81   10.235%   $261.0475   $261.05   $261.05   $261.00  
  Purchase #4 $154.80   4.361%   $161.5508   $161.55   $161.55   $161.60  
  Purchase #5 $250.98   9.366%   $274.4868   $274.49   $274.50   $274.50  
  Purchase #6 $66.64   4.512%   $69.6468   $69.65   $69.65   $69.60  
  Purchase #7 $65.97   4.441%   $68.8997   $68.90   $68.90   $68.90  
  7 purchase totals = $1,023.34       $1,108.5895   $1,108.60   $1,108.60   $1,108.60