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 $67.74   8.177%   $73.2791   $73.28   $73.30   $73.30  
  Purchase #2 $195.65   10.798%   $216.7763   $216.78   $216.80   $216.80  
  Purchase #3 $212.26   12.715%   $239.2489   $239.25   $239.25   $239.20  
  Purchase #4 $169.54   9.255%   $185.2309   $185.23   $185.25   $185.20  
  Purchase #5 $17.59   5.830%   $18.6155   $18.62   $18.60   $18.60  
  Purchase #6 $142.62   11.655%   $159.2424   $159.24   $159.25   $159.20  
  Purchase #7 $216.80   7.756%   $233.615   $233.62   $233.60   $233.60  
  7 purchase totals = $1,022.20       $1,126.0081   $1,126.02   $1,126.05   $1,125.90