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 $215.51   13.515%   $244.6362   $244.64   $244.65   $244.60  
  Purchase #2 $165.55   12.406%   $186.0881   $186.09   $186.10   $186.10  
  Purchase #3 $72.63   4.267%   $75.7291   $75.73   $75.75   $75.70  
  Purchase #4 $31.91   13.337%   $36.1658   $36.17   $36.15   $36.20  
  Purchase #5 $104.36   12.814%   $117.7327   $117.73   $117.75   $117.70  
  Purchase #6 $134.90   4.328%   $140.7385   $140.74   $140.75   $140.70  
  Purchase #7 $200.56   11.465%   $223.5542   $223.55   $223.55   $223.60  
  7 purchase totals = $925.42       $1,024.6446   $1,024.65   $1,024.70   $1,024.60