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	$67.45	12.480%	$75.8678	$75.87	$75.85	$75.90
Purchase #2	$230.34	10.675%	$254.9288	$254.93	$254.95	$254.90
Purchase #3	$103.31	6.389%	$109.9105	$109.91	$109.90	$109.90
Purchase #4	$167.27	9.429%	$183.0419	$183.04	$183.05	$183.00
Purchase #5	$146.84	7.648%	$158.0703	$158.07	$158.05	$158.10
Purchase #6	$158.57	8.585%	$172.1832	$172.18	$172.20	$172.20
Purchase #7	$95.45	13.130%	$107.9826	$107.98	$108.00	$108.00
7 purchase totals =	$969.23		$1,061.9851	$1,061.98	$1,062.00	$1,062.00