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	$143.47	7.201%	$153.8013	$153.80	$153.80	$153.80
Purchase #2	$9.49	10.567%	$10.4928	$10.49	$10.50	$10.50
Purchase #3	$248.72	13.486%	$282.2624	$282.26	$282.25	$282.30
Purchase #4	$175.83	5.717%	$185.8822	$185.88	$185.90	$185.90
Purchase #5	$244.37	12.335%	$274.513	$274.51	$274.50	$274.50
Purchase #6	$136.94	6.744%	$146.1752	$146.18	$146.20	$146.20
Purchase #7	$55.75	5.841%	$59.0064	$59.01	$59.00	$59.00
7 purchase totals =	$1,014.57		$1,112.1333	$1,112.13	$1,112.15	$1,112.20