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	$48.29	4.385%	$50.4075	$50.41	$50.40	$50.40
Purchase #2	$159.54	8.306%	$172.7914	$172.79	$172.80	$172.80
Purchase #3	$86.50	4.341%	$90.255	$90.26	$90.25	$90.30
Purchase #4	$118.90	7.433%	$127.7378	$127.74	$127.75	$127.70
Purchase #5	$221.41	11.821%	$247.5829	$247.58	$247.60	$247.60
Purchase #6	$186.80	11.810%	$208.8611	$208.86	$208.85	$208.90
Purchase #7	$171.66	3.393%	$177.4844	$177.48	$177.50	$177.50
7 purchase totals =	$993.10		$1,075.1201	$1,075.12	$1,075.15	$1,075.20