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 $61.67   10.523%   $68.1595   $68.16   $68.15   $68.20  
  Purchase #2 $243.26   9.566%   $266.5303   $266.53   $266.55   $266.50  
  Purchase #3 $165.92   10.585%   $183.4826   $183.48   $183.50   $183.50  
  Purchase #4 $73.90   10.343%   $81.5435   $81.54   $81.55   $81.50  
  Purchase #5 $15.94   12.187%   $17.8826   $17.88   $17.90   $17.90  
  Purchase #6 $97.94   12.201%   $109.8897   $109.89   $109.90   $109.90  
  Purchase #7 $200.26   6.812%   $213.9017   $213.90   $213.90   $213.90  
  7 purchase totals = $858.89       $941.3899   $941.38   $941.45   $941.40