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 $214.82   7.669%   $231.2945   $231.29   $231.30   $231.30  
  Purchase #2 $49.45   3.517%   $51.1892   $51.19   $51.20   $51.20  
  Purchase #3 $7.92   9.463%   $8.6695   $8.67   $8.65   $8.70  
  Purchase #4 $96.40   5.603%   $101.8013   $101.80   $101.80   $101.80  
  Purchase #5 $178.74   4.691%   $187.1247   $187.12   $187.10   $187.10  
  Purchase #6 $182.77   7.161%   $195.8582   $195.86   $195.85   $195.90  
  Purchase #7 $224.94   9.668%   $246.6872   $246.69   $246.70   $246.70  
  7 purchase totals = $955.04       $1,022.6246   $1,022.62   $1,022.60   $1,022.70