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 $97.47   13.411%   $110.5417   $110.54   $110.55   $110.50  
  Purchase #2 $207.29   9.364%   $226.7006   $226.70   $226.70   $226.70  
  Purchase #3 $169.49   13.411%   $192.2203   $192.22   $192.20   $192.20  
  Purchase #4 $43.63   9.762%   $47.8892   $47.89   $47.90   $47.90  
  Purchase #5 $245.80   7.648%   $264.5988   $264.60   $264.60   $264.60  
  Purchase #6 $57.47   10.245%   $63.3578   $63.36   $63.35   $63.40  
  Purchase #7 $47.25   5.660%   $49.9244   $49.92   $49.90   $49.90  
  7 purchase totals = $868.40       $955.2328   $955.23   $955.20   $955.20