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 $47.84   4.106%   $49.8043   $49.80   $49.80   $49.80  
  Purchase #2 $246.53   11.424%   $274.6936   $274.69   $274.70   $274.70  
  Purchase #3 $168.53   4.788%   $176.5992   $176.60   $176.60   $176.60  
  Purchase #4 $136.47   3.648%   $141.4484   $141.45   $141.45   $141.40  
  Purchase #5 $231.83   4.668%   $242.6518   $242.65   $242.65   $242.70  
  Purchase #6 $116.92   7.774%   $126.0094   $126.01   $126.00   $126.00  
  Purchase #7 $71.25   3.583%   $73.8029   $73.80   $73.80   $73.80  
  7 purchase totals = $1,019.37       $1,085.0096   $1,085.00   $1,085.00   $1,085.00