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 $62.50   7.619%   $67.2619   $67.26   $67.25   $67.30  
  Purchase #2 $248.85   5.612%   $262.8155   $262.82   $262.80   $262.80  
  Purchase #3 $153.42   3.598%   $158.9401   $158.94   $158.95   $158.90  
  Purchase #4 $179.49   5.572%   $189.4912   $189.49   $189.50   $189.50  
  Purchase #5 $157.59   13.149%   $178.3115   $178.31   $178.30   $178.30  
  Purchase #6 $181.76   7.198%   $194.8431   $194.84   $194.85   $194.80  
  Purchase #7 $169.50   3.710%   $175.7885   $175.79   $175.80   $175.80  
  7 purchase totals = $1,153.11       $1,227.4518   $1,227.45   $1,227.45   $1,227.40