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 $162.41   4.369%   $169.5057   $169.51   $169.50   $169.50  
  Purchase #2 $129.38   10.316%   $142.7268   $142.73   $142.75   $142.70  
  Purchase #3 $52.47   6.337%   $55.795   $55.80   $55.80   $55.80  
  Purchase #4 $234.86   13.259%   $266.0001   $266.00   $266.00   $266.00  
  Purchase #5 $95.59   5.827%   $101.16   $101.16   $101.15   $101.20  
  Purchase #6 $116.64   8.600%   $126.671   $126.67   $126.65   $126.70  
  Purchase #7 $89.27   3.635%   $92.515   $92.52   $92.50   $92.50  
  7 purchase totals = $880.62       $954.3736   $954.39   $954.35   $954.40