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 $184.90   11.212%   $205.631   $205.63   $205.65   $205.60  
  Purchase #2 $193.82   10.441%   $214.0567   $214.06   $214.05   $214.10  
  Purchase #3 $245.67   8.175%   $265.7535   $265.75   $265.75   $265.80  
  Purchase #4 $152.36   8.595%   $165.4553   $165.46   $165.45   $165.50  
  Purchase #5 $201.29   6.366%   $214.1041   $214.10   $214.10   $214.10  
  Purchase #6 $185.66   9.844%   $203.9364   $203.94   $203.95   $203.90  
  Purchase #7 $194.30   11.127%   $215.9198   $215.92   $215.90   $215.90  
  7 purchase totals = $1,358.00       $1,484.8568   $1,484.86   $1,484.85   $1,484.90