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 $194.87   6.713%   $207.9516   $207.95   $207.95   $208.00  
  Purchase #2 $115.57   12.641%   $130.1792   $130.18   $130.20   $130.20  
  Purchase #3 $231.51   12.826%   $261.2035   $261.20   $261.20   $261.20  
  Purchase #4 $61.71   8.331%   $66.8511   $66.85   $66.85   $66.90  
  Purchase #5 $205.47   8.583%   $223.1055   $223.11   $223.10   $223.10  
  Purchase #6 $143.86   3.695%   $149.1756   $149.18   $149.20   $149.20  
  Purchase #7 $133.36   8.727%   $144.9983   $145.00   $145.00   $145.00  
  7 purchase totals = $1,086.35       $1,183.4648   $1,183.47   $1,183.50   $1,183.60