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 $174.67   4.211%   $182.0254   $182.03   $182.05   $182.00  
  Purchase #2 $162.66   12.727%   $183.3617   $183.36   $183.35   $183.40  
  Purchase #3 $70.90   4.488%   $74.082   $74.08   $74.10   $74.10  
  Purchase #4 $83.93   11.740%   $93.7834   $93.78   $93.80   $93.80  
  Purchase #5 $112.82   10.139%   $124.2588   $124.26   $124.25   $124.30  
  Purchase #6 $206.41   3.873%   $214.4043   $214.40   $214.40   $214.40  
  Purchase #7 $68.39   9.153%   $74.6497   $74.65   $74.65   $74.60  
  7 purchase totals = $879.78       $946.5653   $946.56   $946.60   $946.60