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 $43.64   5.732%   $46.1414   $46.14   $46.15   $46.10  
  Purchase #2 $30.33   5.541%   $32.0106   $32.01   $32.00   $32.00  
  Purchase #3 $178.99   4.451%   $186.9568   $186.96   $186.95   $187.00  
  Purchase #4 $186.47   4.582%   $195.0141   $195.01   $195.00   $195.00  
  Purchase #5 $32.36   5.178%   $34.0356   $34.04   $34.05   $34.00  
  Purchase #6 $244.70   8.859%   $266.378   $266.38   $266.40   $266.40  
  Purchase #7 $148.66   5.394%   $156.6787   $156.68   $156.70   $156.70  
  7 purchase totals = $865.15       $917.2152   $917.22   $917.25   $917.20