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 $195.53   8.347%   $211.8509   $211.85   $211.85   $211.90  
  Purchase #2 $24.99   4.515%   $26.1183   $26.12   $26.10   $26.10  
  Purchase #3 $161.38   13.509%   $183.1808   $183.18   $183.20   $183.20  
  Purchase #4 $240.27   5.106%   $252.5382   $252.54   $252.55   $252.50  
  Purchase #5 $91.26   4.845%   $95.6815   $95.68   $95.70   $95.70  
  Purchase #6 $124.47   4.744%   $130.3749   $130.37   $130.35   $130.40  
  Purchase #7 $148.58   9.174%   $162.2107   $162.21   $162.20   $162.20  
  7 purchase totals = $986.48       $1,061.9553   $1,061.95   $1,061.95   $1,062.00