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 $65.66   11.490%   $73.2043   $73.20   $73.20   $73.20  
  Purchase #2 $212.51   12.850%   $239.8175   $239.82   $239.80   $239.80  
  Purchase #3 $213.61   3.626%   $221.3555   $221.36   $221.35   $221.40  
  Purchase #4 $206.63   3.549%   $213.9633   $213.96   $213.95   $214.00  
  Purchase #5 $189.58   13.272%   $214.7411   $214.74   $214.75   $214.70  
  Purchase #6 $64.49   13.616%   $73.271   $73.27   $73.25   $73.30  
  Purchase #7 $184.47   13.846%   $210.0117   $210.01   $210.00   $210.00  
  7 purchase totals = $1,136.95       $1,246.3644   $1,246.36   $1,246.30   $1,246.40