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	$133.55	7.445%	$143.4928	$143.49	$143.50	$143.50
Purchase #2	$84.72	7.276%	$90.8842	$90.88	$90.90	$90.90
Purchase #3	$17.78	12.185%	$19.9465	$19.95	$19.95	$19.90
Purchase #4	$49.29	3.605%	$51.0669	$51.07	$51.05	$51.10
Purchase #5	$217.93	5.278%	$229.4323	$229.43	$229.45	$229.40
Purchase #6	$194.41	11.560%	$216.8838	$216.88	$216.90	$216.90
Purchase #7	$32.26	4.123%	$33.5901	$33.59	$33.60	$33.60
7 purchase totals =	$729.94		$785.2966	$785.29	$785.35	$785.30