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 $244.39   7.356%   $262.3673   $262.37   $262.35   $262.40  
  Purchase #2 $67.37   9.242%   $73.5963   $73.60   $73.60   $73.60  
  Purchase #3 $100.86   13.428%   $114.4035   $114.40   $114.40   $114.40  
  Purchase #4 $242.44   12.358%   $272.4007   $272.40   $272.40   $272.40  
  Purchase #5 $194.73   13.362%   $220.7498   $220.75   $220.75   $220.70  
  Purchase #6 $64.25   13.669%   $73.0323   $73.03   $73.05   $73.00  
  Purchase #7 $114.73   4.808%   $120.2462   $120.25   $120.25   $120.20  
  7 purchase totals = $1,028.77       $1,136.7961   $1,136.80   $1,136.80   $1,136.70