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	$182.67	4.286%	$190.4992	$190.50	$190.50	$190.50
Purchase #2	$93.90	6.367%	$99.8786	$99.88	$99.90	$99.90
Purchase #3	$242.25	4.599%	$253.3911	$253.39	$253.40	$253.40
Purchase #4	$205.92	4.299%	$214.7725	$214.77	$214.75	$214.80
Purchase #5	$32.82	11.543%	$36.6084	$36.61	$36.60	$36.60
Purchase #6	$61.62	6.323%	$65.5162	$65.52	$65.50	$65.50
Purchase #7	$43.78	7.476%	$47.053	$47.05	$47.05	$47.10
7 purchase totals =	$862.96		$907.7190	$907.72	$907.70	$907.80