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	$241.95	13.242%	$273.989	$273.99	$274.00	$274.00
Purchase #2	$239.67	11.371%	$266.9229	$266.92	$266.90	$266.90
Purchase #3	$229.61	11.247%	$255.4342	$255.43	$255.45	$255.40
Purchase #4	$147.87	5.162%	$155.503	$155.50	$155.50	$155.50
Purchase #5	$148.69	13.456%	$168.6977	$168.70	$168.70	$168.70
Purchase #6	$36.55	3.489%	$37.8252	$37.83	$37.85	$37.80
Purchase #7	$46.98	7.445%	$50.4777	$50.48	$50.50	$50.50
7 purchase totals =	$1,091.32		$1,208.8497	$1,208.85	$1,208.90	$1,208.80