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 $71.57   3.725%   $74.236   $74.24   $74.25   $74.20  
  Purchase #2 $241.97   8.250%   $261.9325   $261.93   $261.95   $261.90  
  Purchase #3 $236.63   6.871%   $252.8888   $252.89   $252.90   $252.90  
  Purchase #4 $47.51   9.505%   $52.0258   $52.03   $52.05   $52.00  
  Purchase #5 $106.84   9.571%   $117.0657   $117.07   $117.05   $117.10  
  Purchase #6 $159.93   12.665%   $180.1851   $180.19   $180.20   $180.20  
  Purchase #7 $89.91   5.679%   $95.016   $95.02   $95.00   $95.00  
  7 purchase totals = $954.36       $1,033.3499   $1,033.37   $1,033.40   $1,033.30