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 $192.68   11.325%   $214.501   $214.50   $214.50   $214.50  
  Purchase #2 $59.69   3.250%   $61.6299   $61.63   $61.65   $61.60  
  Purchase #3 $20.76   10.183%   $22.874   $22.87   $22.85   $22.90  
  Purchase #4 $55.46   9.343%   $60.6416   $60.64   $60.65   $60.60  
  Purchase #5 $161.63   11.144%   $179.642   $179.64   $179.65   $179.60  
  Purchase #6 $157.51   12.238%   $176.7861   $176.79   $176.80   $176.80  
  Purchase #7 $73.89   10.340%   $81.5302   $81.53   $81.55   $81.50  
  7 purchase totals = $721.62       $797.6048   $797.60   $797.65   $797.50