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 $98.44   4.359%   $102.731   $102.73   $102.75   $102.70  
  Purchase #2 $24.89   4.250%   $25.9478   $25.95   $25.95   $25.90  
  Purchase #3 $42.78   8.269%   $46.3175   $46.32   $46.30   $46.30  
  Purchase #4 $201.36   8.471%   $218.4172   $218.42   $218.40   $218.40  
  Purchase #5 $240.93   3.769%   $250.0107   $250.01   $250.00   $250.00  
  Purchase #6 $242.57   10.752%   $268.6511   $268.65   $268.65   $268.70  
  Purchase #7 $170.82   7.132%   $183.0029   $183.00   $183.00   $183.00  
  7 purchase totals = $1,021.79       $1,095.0782   $1,095.08   $1,095.05   $1,095.00