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 $91.69   4.697%   $95.9967   $96.00   $96.00   $96.00  
  Purchase #2 $234.99   5.719%   $248.4291   $248.43   $248.45   $248.40  
  Purchase #3 $112.44   3.690%   $116.589   $116.59   $116.60   $116.60  
  Purchase #4 $97.55   5.511%   $102.926   $102.93   $102.95   $102.90  
  Purchase #5 $143.91   12.511%   $161.9146   $161.91   $161.90   $161.90  
  Purchase #6 $130.62   7.407%   $140.295   $140.30   $140.30   $140.30  
  Purchase #7 $198.86   4.394%   $207.5979   $207.60   $207.60   $207.60  
  7 purchase totals = $1,010.06       $1,073.7483   $1,073.76   $1,073.80   $1,073.70