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 $187.26   9.868%   $205.7388   $205.74   $205.75   $205.70  
  Purchase #2 $158.91   12.392%   $178.6021   $178.60   $178.60   $178.60  
  Purchase #3 $11.74   8.872%   $12.7816   $12.78   $12.80   $12.80  
  Purchase #4 $146.67   3.435%   $151.7081   $151.71   $151.70   $151.70  
  Purchase #5 $219.38   4.109%   $228.3943   $228.39   $228.40   $228.40  
  Purchase #6 $242.74   9.376%   $265.4993   $265.50   $265.50   $265.50  
  Purchase #7 $242.87   7.418%   $260.8861   $260.89   $260.90   $260.90  
  7 purchase totals = $1,209.57       $1,303.6103   $1,303.61   $1,303.65   $1,303.60