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 $163.28   10.729%   $180.7983   $180.80   $180.80   $180.80  
  Purchase #2 $225.71   9.323%   $246.7529   $246.75   $246.75   $246.80  
  Purchase #3 $98.61   7.841%   $106.342   $106.34   $106.35   $106.30  
  Purchase #4 $153.91   7.874%   $166.0289   $166.03   $166.05   $166.00  
  Purchase #5 $194.92   5.714%   $206.0577   $206.06   $206.05   $206.10  
  Purchase #6 $50.62   5.491%   $53.3995   $53.40   $53.40   $53.40  
  Purchase #7 $7.93   4.674%   $8.3006   $8.30   $8.30   $8.30  
  7 purchase totals = $894.98       $967.6799   $967.68   $967.70   $967.70