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 $114.80   9.798%   $126.0481   $126.05   $126.05   $126.00  
  Purchase #2 $64.59   6.456%   $68.7599   $68.76   $68.75   $68.80  
  Purchase #3 $24.28   10.690%   $26.8755   $26.88   $26.90   $26.90  
  Purchase #4 $96.60   12.115%   $108.3031   $108.30   $108.30   $108.30  
  Purchase #5 $176.62   10.385%   $194.962   $194.96   $194.95   $195.00  
  Purchase #6 $117.55   11.687%   $131.2881   $131.29   $131.30   $131.30  
  Purchase #7 $153.68   10.813%   $170.2974   $170.30   $170.30   $170.30  
  7 purchase totals = $748.12       $826.5341   $826.54   $826.55   $826.60