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 $84.69   13.116%   $95.7979   $95.80   $95.80   $95.80  
  Purchase #2 $206.34   7.140%   $221.0727   $221.07   $221.05   $221.10  
  Purchase #3 $175.73   9.397%   $192.2433   $192.24   $192.25   $192.20  
  Purchase #4 $236.80   3.326%   $244.676   $244.68   $244.70   $244.70  
  Purchase #5 $162.74   6.108%   $172.6802   $172.68   $172.70   $172.70  
  Purchase #6 $229.76   7.234%   $246.3808   $246.38   $246.40   $246.40  
  Purchase #7 $83.75   7.287%   $89.8529   $89.85   $89.85   $89.90  
  7 purchase totals = $1,179.81       $1,262.7038   $1,262.70   $1,262.75   $1,262.80