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 $62.47   8.349%   $67.6856   $67.69   $67.70   $67.70  
  Purchase #2 $225.77   3.463%   $233.5884   $233.59   $233.60   $233.60  
  Purchase #3 $198.43   7.812%   $213.9314   $213.93   $213.95   $213.90  
  Purchase #4 $154.78   12.566%   $174.2297   $174.23   $174.25   $174.20  
  Purchase #5 $99.99   4.421%   $104.4106   $104.41   $104.40   $104.40  
  Purchase #6 $26.67   11.598%   $29.7632   $29.76   $29.75   $29.80  
  Purchase #7 $45.31   4.851%   $47.508   $47.51   $47.50   $47.50  
  7 purchase totals = $813.42       $871.1169   $871.12   $871.15   $871.10