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	$126.25	11.859%	$141.222	$141.22	$141.20	$141.20
Purchase #2	$164.57	6.572%	$175.3855	$175.39	$175.40	$175.40
Purchase #3	$38.64	12.853%	$43.6064	$43.61	$43.60	$43.60
Purchase #4	$94.44	11.657%	$105.4489	$105.45	$105.45	$105.40
Purchase #5	$240.29	4.635%	$251.4274	$251.43	$251.45	$251.40
Purchase #6	$179.42	7.649%	$193.1438	$193.14	$193.15	$193.10
Purchase #7	$145.73	13.453%	$165.3351	$165.34	$165.35	$165.30
7 purchase totals =	$989.34		$1,075.5691	$1,075.58	$1,075.60	$1,075.40