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 $141.65   7.682%   $152.5316   $152.53   $152.55   $152.50  
  Purchase #2 $107.26   11.538%   $119.6357   $119.64   $119.65   $119.60  
  Purchase #3 $194.48   5.399%   $204.98   $204.98   $205.00   $205.00  
  Purchase #4 $71.61   13.522%   $81.2931   $81.29   $81.30   $81.30  
  Purchase #5 $41.69   3.757%   $43.2563   $43.26   $43.25   $43.30  
  Purchase #6 $170.74   13.331%   $193.5013   $193.50   $193.50   $193.50  
  Purchase #7 $68.89   3.542%   $71.3301   $71.33   $71.35   $71.30  
  7 purchase totals = $796.32       $866.5281   $866.53   $866.60   $866.50