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 $56.26   11.496%   $62.7276   $62.73   $62.75   $62.70  
  Purchase #2 $121.26   4.738%   $127.0053   $127.01   $127.00   $127.00  
  Purchase #3 $69.74   9.221%   $76.1707   $76.17   $76.15   $76.20  
  Purchase #4 $163.85   12.103%   $183.6808   $183.68   $183.70   $183.70  
  Purchase #5 $239.38   7.809%   $258.0732   $258.07   $258.05   $258.10  
  Purchase #6 $40.81   4.477%   $42.6371   $42.64   $42.65   $42.60  
  Purchase #7 $117.48   4.651%   $122.944   $122.94   $122.95   $122.90  
  7 purchase totals = $808.78       $873.2387   $873.24   $873.25   $873.20