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 $61.49   7.175%   $65.9019   $65.90   $65.90   $65.90  
  Purchase #2 $206.64   5.636%   $218.2862   $218.29   $218.30   $218.30  
  Purchase #3 $48.96   4.513%   $51.1696   $51.17   $51.15   $51.20  
  Purchase #4 $20.65   8.794%   $22.466   $22.47   $22.45   $22.50  
  Purchase #5 $58.40   4.201%   $60.8534   $60.85   $60.85   $60.90  
  Purchase #6 $246.67   6.200%   $261.9635   $261.96   $261.95   $262.00  
  Purchase #7 $80.88   4.111%   $84.205   $84.21   $84.20   $84.20  
  7 purchase totals = $723.69       $764.8456   $764.85   $764.80   $765.00