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 $58.81   8.235%   $63.653   $63.65   $63.65   $63.70  
  Purchase #2 $78.89   9.757%   $86.5873   $86.59   $86.60   $86.60  
  Purchase #3 $158.47   5.407%   $167.0385   $167.04   $167.05   $167.00  
  Purchase #4 $179.86   12.744%   $202.7814   $202.78   $202.80   $202.80  
  Purchase #5 $162.60   6.544%   $173.2405   $173.24   $173.25   $173.20  
  Purchase #6 $142.57   13.854%   $162.3216   $162.32   $162.30   $162.30  
  Purchase #7 $170.86   8.846%   $185.9743   $185.97   $185.95   $186.00  
  7 purchase totals = $952.06       $1,041.5966   $1,041.59   $1,041.60   $1,041.60