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 $180.96   7.232%   $194.047   $194.05   $194.05   $194.00  
  Purchase #2 $85.43   5.154%   $89.8331   $89.83   $89.85   $89.80  
  Purchase #3 $108.80   4.742%   $113.9593   $113.96   $113.95   $114.00  
  Purchase #4 $126.99   7.172%   $136.0977   $136.10   $136.10   $136.10  
  Purchase #5 $185.73   13.662%   $211.1044   $211.10   $211.10   $211.10  
  Purchase #6 $109.96   6.186%   $116.7621   $116.76   $116.75   $116.80  
  Purchase #7 $242.47   10.244%   $267.3086   $267.31   $267.30   $267.30  
  7 purchase totals = $1,040.34       $1,129.1122   $1,129.11   $1,129.10   $1,129.10