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 $197.45   8.557%   $214.3458   $214.35   $214.35   $214.30  
  Purchase #2 $32.98   5.149%   $34.6781   $34.68   $34.70   $34.70  
  Purchase #3 $52.90   13.345%   $59.9595   $59.96   $59.95   $60.00  
  Purchase #4 $89.98   12.441%   $101.1744   $101.17   $101.15   $101.20  
  Purchase #5 $210.74   9.104%   $229.9258   $229.93   $229.95   $229.90  
  Purchase #6 $223.48   9.508%   $244.7285   $244.73   $244.75   $244.70  
  Purchase #7 $208.55   4.527%   $217.9911   $217.99   $218.00   $218.00  
  7 purchase totals = $1,016.08       $1,102.8032   $1,102.81   $1,102.85   $1,102.80