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 $205.52   4.126%   $213.9998   $214.00   $214.00   $214.00  
  Purchase #2 $248.88   4.487%   $260.0472   $260.05   $260.05   $260.00  
  Purchase #3 $241.55   8.845%   $262.9151   $262.92   $262.90   $262.90  
  Purchase #4 $131.64   9.679%   $144.3814   $144.38   $144.40   $144.40  
  Purchase #5 $120.39   5.454%   $126.9561   $126.96   $126.95   $127.00  
  Purchase #6 $180.38   4.197%   $187.9505   $187.95   $187.95   $188.00  
  Purchase #7 $69.34   3.589%   $71.8286   $71.83   $71.85   $71.80  
  7 purchase totals = $1,197.70       $1,268.0787   $1,268.09   $1,268.10   $1,268.10