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	$241.77	13.682%	$274.849	$274.85	$274.85	$274.80
Purchase #2	$209.28	7.676%	$225.3443	$225.34	$225.35	$225.30
Purchase #3	$154.83	7.758%	$166.8417	$166.84	$166.85	$166.80
Purchase #4	$147.80	13.313%	$167.4766	$167.48	$167.50	$167.50
Purchase #5	$138.70	3.295%	$143.2702	$143.27	$143.25	$143.30
Purchase #6	$162.46	3.842%	$168.7017	$168.70	$168.70	$168.70
Purchase #7	$172.28	8.503%	$186.929	$186.93	$186.95	$186.90
7 purchase totals =	$1,227.12		$1,333.4125	$1,333.41	$1,333.45	$1,333.30