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 $59.42   13.651%   $67.5314   $67.53   $67.55   $67.50  
  Purchase #2 $248.60   5.411%   $262.0517   $262.05   $262.05   $262.10  
  Purchase #3 $28.49   7.660%   $30.6723   $30.67   $30.65   $30.70  
  Purchase #4 $200.71   4.604%   $209.9507   $209.95   $209.95   $210.00  
  Purchase #5 $214.87   11.637%   $239.8744   $239.87   $239.85   $239.90  
  Purchase #6 $96.61   10.838%   $107.0806   $107.08   $107.10   $107.10  
  Purchase #7 $149.36   7.480%   $160.5321   $160.53   $160.55   $160.50  
  7 purchase totals = $998.06       $1,077.6932   $1,077.68   $1,077.70   $1,077.80