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 $244.57   9.481%   $267.7577   $267.76   $267.75   $267.80  
  Purchase #2 $93.90   3.206%   $96.9104   $96.91   $96.90   $96.90  
  Purchase #3 $183.53   10.594%   $202.9732   $202.97   $202.95   $203.00  
  Purchase #4 $121.57   7.808%   $131.0622   $131.06   $131.05   $131.10  
  Purchase #5 $82.68   4.447%   $86.3568   $86.36   $86.35   $86.40  
  Purchase #6 $162.88   3.256%   $168.1834   $168.18   $168.20   $168.20  
  Purchase #7 $161.99   13.401%   $183.6983   $183.70   $183.70   $183.70  
  7 purchase totals = $1,051.12       $1,136.9420   $1,136.94   $1,136.90   $1,137.10