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 $148.64   10.121%   $163.6839   $163.68   $163.70   $163.70  
  Purchase #2 $57.96   4.799%   $60.7415   $60.74   $60.75   $60.70  
  Purchase #3 $248.28   6.283%   $263.8794   $263.88   $263.90   $263.90  
  Purchase #4 $193.75   4.141%   $201.7732   $201.77   $201.75   $201.80  
  Purchase #5 $195.29   6.152%   $207.3042   $207.30   $207.30   $207.30  
  Purchase #6 $208.58   13.858%   $237.485   $237.49   $237.50   $237.50  
  Purchase #7 $14.57   13.793%   $16.5796   $16.58   $16.60   $16.60  
  7 purchase totals = $1,067.07       $1,151.4468   $1,151.44   $1,151.50   $1,151.50