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 $45.29   5.143%   $47.6193   $47.62   $47.60   $47.60  
  Purchase #2 $152.81   4.201%   $159.2295   $159.23   $159.25   $159.20  
  Purchase #3 $85.70   9.565%   $93.8972   $93.90   $93.90   $93.90  
  Purchase #4 $124.69   8.124%   $134.8198   $134.82   $134.80   $134.80  
  Purchase #5 $243.34   3.327%   $251.4359   $251.44   $251.45   $251.40  
  Purchase #6 $186.73   4.738%   $195.5773   $195.58   $195.60   $195.60  
  Purchase #7 $239.81   11.246%   $266.779   $266.78   $266.80   $266.80  
  7 purchase totals = $1,078.37       $1,149.3580   $1,149.37   $1,149.40   $1,149.30