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 $194.30   4.662%   $203.3583   $203.36   $203.35   $203.40  
  Purchase #2 $239.88   3.254%   $247.6857   $247.69   $247.70   $247.70  
  Purchase #3 $240.27   8.249%   $260.0899   $260.09   $260.10   $260.10  
  Purchase #4 $152.92   5.538%   $161.3887   $161.39   $161.40   $161.40  
  Purchase #5 $236.31   10.634%   $261.4392   $261.44   $261.45   $261.40  
  Purchase #6 $182.36   5.867%   $193.0591   $193.06   $193.05   $193.10  
  Purchase #7 $145.83   8.658%   $158.456   $158.46   $158.45   $158.50  
  7 purchase totals = $1,391.87       $1,485.4769   $1,485.49   $1,485.50   $1,485.60