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 $88.68   9.684%   $97.2678   $97.27   $97.25   $97.30  
  Purchase #2 $189.73   3.593%   $196.547   $196.55   $196.55   $196.50  
  Purchase #3 $13.39   12.227%   $15.0272   $15.03   $15.05   $15.00  
  Purchase #4 $188.36   9.439%   $206.1393   $206.14   $206.15   $206.10  
  Purchase #5 $170.95   13.415%   $193.8829   $193.88   $193.90   $193.90  
  Purchase #6 $25.43   3.153%   $26.2318   $26.23   $26.25   $26.20  
  Purchase #7 $20.37   11.162%   $22.6437   $22.64   $22.65   $22.60  
  7 purchase totals = $696.91       $757.7397   $757.74   $757.80   $757.60