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 $72.57   5.554%   $76.6005   $76.60   $76.60   $76.60  
  Purchase #2 $242.73   5.135%   $255.1942   $255.19   $255.20   $255.20  
  Purchase #3 $96.36   7.846%   $103.9204   $103.92   $103.90   $103.90  
  Purchase #4 $237.88   3.494%   $246.1915   $246.19   $246.20   $246.20  
  Purchase #5 $179.49   10.679%   $198.6577   $198.66   $198.65   $198.70  
  Purchase #6 $159.36   11.110%   $177.0649   $177.06   $177.05   $177.10  
  Purchase #7 $92.81   11.235%   $103.2372   $103.24   $103.25   $103.20  
  7 purchase totals = $1,081.20       $1,160.8664   $1,160.86   $1,160.85   $1,160.90