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 $41.25   4.668%   $43.1756   $43.18   $43.20   $43.20  
  Purchase #2 $150.87   12.199%   $169.2746   $169.27   $169.25   $169.30  
  Purchase #3 $170.93   6.789%   $182.5344   $182.53   $182.55   $182.50  
  Purchase #4 $32.81   8.827%   $35.7061   $35.71   $35.70   $35.70  
  Purchase #5 $213.84   13.140%   $241.9386   $241.94   $241.95   $241.90  
  Purchase #6 $126.28   8.198%   $136.6324   $136.63   $136.65   $136.60  
  Purchase #7 $50.96   4.185%   $53.0927   $53.09   $53.10   $53.10  
  7 purchase totals = $786.94       $862.3544   $862.35   $862.40   $862.30