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 $32.92   5.807%   $34.8317   $34.83   $34.85   $34.80  
  Purchase #2 $197.43   6.620%   $210.4999   $210.50   $210.50   $210.50  
  Purchase #3 $106.96   7.412%   $114.8879   $114.89   $114.90   $114.90  
  Purchase #4 $219.48   8.421%   $237.9624   $237.96   $237.95   $238.00  
  Purchase #5 $236.97   5.123%   $249.11   $249.11   $249.10   $249.10  
  Purchase #6 $149.95   5.366%   $157.9963   $158.00   $158.00   $158.00  
  Purchase #7 $58.74   7.429%   $63.1038   $63.10   $63.10   $63.10  
  7 purchase totals = $1,002.45       $1,068.3920   $1,068.39   $1,068.40   $1,068.40