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 $67.48   8.465%   $73.1922   $73.19   $73.20   $73.20  
  Purchase #2 $177.74   3.149%   $183.337   $183.34   $183.35   $183.30  
  Purchase #3 $41.43   6.763%   $44.2319   $44.23   $44.25   $44.20  
  Purchase #4 $70.30   8.788%   $76.478   $76.48   $76.50   $76.50  
  Purchase #5 $199.66   13.276%   $226.1669   $226.17   $226.15   $226.20  
  Purchase #6 $197.38   11.655%   $220.3846   $220.38   $220.40   $220.40  
  Purchase #7 $17.68   8.469%   $19.1773   $19.18   $19.20   $19.20  
  7 purchase totals = $771.67       $842.9679   $842.97   $843.05   $843.00