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 $182.93   6.195%   $194.2625   $194.26   $194.25   $194.30  
  Purchase #2 $156.96   10.733%   $173.8065   $173.81   $173.80   $173.80  
  Purchase #3 $33.95   4.854%   $35.5979   $35.60   $35.60   $35.60  
  Purchase #4 $245.77   13.235%   $278.2977   $278.30   $278.30   $278.30  
  Purchase #5 $64.70   12.208%   $72.5986   $72.60   $72.60   $72.60  
  Purchase #6 $145.74   5.268%   $153.4176   $153.42   $153.40   $153.40  
  Purchase #7 $188.89   11.691%   $210.9731   $210.97   $210.95   $211.00  
  7 purchase totals = $1,018.94       $1,118.9539   $1,118.96   $1,118.90   $1,119.00