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 $214.87   5.442%   $226.5632   $226.56   $226.55   $226.60  
  Purchase #2 $247.81   6.191%   $263.1519   $263.15   $263.15   $263.20  
  Purchase #3 $101.69   9.658%   $111.5112   $111.51   $111.50   $111.50  
  Purchase #4 $151.73   5.659%   $160.3164   $160.32   $160.30   $160.30  
  Purchase #5 $80.86   4.751%   $84.7017   $84.70   $84.70   $84.70  
  Purchase #6 $226.88   4.491%   $237.0692   $237.07   $237.05   $237.10  
  Purchase #7 $238.99   10.689%   $264.5356   $264.54   $264.55   $264.50  
  7 purchase totals = $1,262.83       $1,347.8492   $1,347.85   $1,347.80   $1,347.90