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 $192.73   11.379%   $214.6607   $214.66   $214.65   $214.70  
  Purchase #2 $27.55   8.152%   $29.7959   $29.80   $29.80   $29.80  
  Purchase #3 $144.43   11.348%   $160.8199   $160.82   $160.80   $160.80  
  Purchase #4 $76.89   13.497%   $87.2678   $87.27   $87.25   $87.30  
  Purchase #5 $204.97   5.646%   $216.5426   $216.54   $216.55   $216.50  
  Purchase #6 $248.36   13.523%   $281.9457   $281.95   $281.95   $281.90  
  Purchase #7 $21.33   8.646%   $23.1742   $23.17   $23.15   $23.20  
  7 purchase totals = $916.26       $1,014.2068   $1,014.21   $1,014.15   $1,014.20