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 $215.82   11.852%   $241.399   $241.40   $241.40   $241.40  
  Purchase #2 $32.83   9.516%   $35.9541   $35.95   $35.95   $36.00  
  Purchase #3 $150.76   4.472%   $157.502   $157.50   $157.50   $157.50  
  Purchase #4 $108.74   5.377%   $114.5869   $114.59   $114.60   $114.60  
  Purchase #5 $242.58   3.340%   $250.6822   $250.68   $250.70   $250.70  
  Purchase #6 $192.52   11.805%   $215.247   $215.25   $215.25   $215.20  
  Purchase #7 $145.84   7.366%   $156.5826   $156.58   $156.60   $156.60  
  7 purchase totals = $1,089.09       $1,171.9538   $1,171.95   $1,172.00   $1,172.00