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 $201.37   6.111%   $213.6757   $213.68   $213.70   $213.70  
  Purchase #2 $195.60   7.617%   $210.4989   $210.50   $210.50   $210.50  
  Purchase #3 $94.35   4.769%   $98.8496   $98.85   $98.85   $98.80  
  Purchase #4 $152.63   13.124%   $172.6612   $172.66   $172.65   $172.70  
  Purchase #5 $216.47   6.782%   $231.151   $231.15   $231.15   $231.20  
  Purchase #6 $177.85   8.489%   $192.9477   $192.95   $192.95   $192.90  
  Purchase #7 $230.41   6.716%   $245.8843   $245.88   $245.90   $245.90  
  7 purchase totals = $1,268.68       $1,365.6684   $1,365.67   $1,365.70   $1,365.70