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 $68.75   4.714%   $71.9909   $71.99   $72.00   $72.00  
  Purchase #2 $112.98   11.440%   $125.9049   $125.90   $125.90   $125.90  
  Purchase #3 $115.65   7.618%   $124.4602   $124.46   $124.45   $124.50  
  Purchase #4 $206.63   5.678%   $218.3625   $218.36   $218.35   $218.40  
  Purchase #5 $58.83   4.701%   $61.5956   $61.60   $61.60   $61.60  
  Purchase #6 $75.84   10.411%   $83.7357   $83.74   $83.75   $83.70  
  Purchase #7 $110.38   5.563%   $116.5204   $116.52   $116.50   $116.50  
  7 purchase totals = $749.06       $802.5702   $802.57   $802.55   $802.60