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 $214.38   9.736%   $235.252   $235.25   $235.25   $235.30  
  Purchase #2 $248.66   10.567%   $274.9359   $274.94   $274.95   $274.90  
  Purchase #3 $172.58   7.174%   $184.9609   $184.96   $184.95   $185.00  
  Purchase #4 $165.88   6.103%   $176.0037   $176.00   $176.00   $176.00  
  Purchase #5 $213.35   13.420%   $241.9816   $241.98   $242.00   $242.00  
  Purchase #6 $95.62   13.813%   $108.828   $108.83   $108.85   $108.80  
  Purchase #7 $208.68   8.198%   $225.7876   $225.79   $225.80   $225.80  
  7 purchase totals = $1,319.15       $1,447.7497   $1,447.75   $1,447.80   $1,447.80