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 $231.90   13.361%   $262.8842   $262.88   $262.90   $262.90  
  Purchase #2 $118.99   5.210%   $125.1894   $125.19   $125.20   $125.20  
  Purchase #3 $46.71   5.346%   $49.2071   $49.21   $49.20   $49.20  
  Purchase #4 $98.38   13.187%   $111.3534   $111.35   $111.35   $111.40  
  Purchase #5 $164.47   13.837%   $187.2277   $187.23   $187.25   $187.20  
  Purchase #6 $204.84   8.793%   $222.8516   $222.85   $222.85   $222.90  
  Purchase #7 $141.64   11.469%   $157.8847   $157.88   $157.90   $157.90  
  7 purchase totals = $1,006.93       $1,116.5981   $1,116.59   $1,116.65   $1,116.70