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 $112.95   11.760%   $126.2329   $126.23   $126.25   $126.20  
  Purchase #2 $174.57   6.159%   $185.3218   $185.32   $185.30   $185.30  
  Purchase #3 $217.50   12.559%   $244.8158   $244.82   $244.80   $244.80  
  Purchase #4 $233.99   3.242%   $241.576   $241.58   $241.60   $241.60  
  Purchase #5 $173.74   11.411%   $193.5655   $193.57   $193.55   $193.60  
  Purchase #6 $196.39   13.111%   $222.1387   $222.14   $222.15   $222.10  
  Purchase #7 $158.80   5.592%   $167.6801   $167.68   $167.70   $167.70  
  7 purchase totals = $1,267.94       $1,381.3308   $1,381.34   $1,381.35   $1,381.30