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 $45.47   4.798%   $47.6517   $47.65   $47.65   $47.70  
  Purchase #2 $6.91   10.155%   $7.6117   $7.61   $7.60   $7.60  
  Purchase #3 $94.63   8.233%   $102.4209   $102.42   $102.40   $102.40  
  Purchase #4 $228.96   5.613%   $241.8115   $241.81   $241.80   $241.80  
  Purchase #5 $203.52   3.326%   $210.2891   $210.29   $210.30   $210.30  
  Purchase #6 $202.58   3.849%   $210.3773   $210.38   $210.40   $210.40  
  Purchase #7 $55.48   11.793%   $62.0228   $62.02   $62.00   $62.00  
  7 purchase totals = $837.55       $882.1850   $882.18   $882.15   $882.20