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 $162.39   5.441%   $171.2256   $171.23   $171.25   $171.20  
  Purchase #2 $232.97   10.618%   $257.7068   $257.71   $257.70   $257.70  
  Purchase #3 $66.76   4.294%   $69.6267   $69.63   $69.65   $69.60  
  Purchase #4 $168.33   6.542%   $179.3421   $179.34   $179.35   $179.30  
  Purchase #5 $11.87   6.769%   $12.6735   $12.67   $12.65   $12.70  
  Purchase #6 $192.90   13.482%   $218.9068   $218.91   $218.90   $218.90  
  Purchase #7 $130.42   4.278%   $135.9994   $136.00   $136.00   $136.00  
  7 purchase totals = $965.64       $1,045.4809   $1,045.49   $1,045.50   $1,045.40