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 $60.59   3.369%   $62.6313   $62.63   $62.65   $62.60  
  Purchase #2 $144.30   4.810%   $151.2408   $151.24   $151.25   $151.20  
  Purchase #3 $13.69   6.775%   $14.6175   $14.62   $14.60   $14.60  
  Purchase #4 $183.51   4.625%   $191.9973   $192.00   $192.00   $192.00  
  Purchase #5 $210.40   8.547%   $228.3829   $228.38   $228.40   $228.40  
  Purchase #6 $237.40   3.612%   $245.9749   $245.97   $245.95   $246.00  
  Purchase #7 $175.42   10.670%   $194.1373   $194.14   $194.15   $194.10  
  7 purchase totals = $1,025.31       $1,088.9820   $1,088.98   $1,089.00   $1,088.90