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	$10.60	4.328%	$11.0588	$11.06	$11.05	$11.10
Purchase #2	$167.47	9.430%	$183.2624	$183.26	$183.25	$183.30
Purchase #3	$218.35	13.525%	$247.8818	$247.88	$247.90	$247.90
Purchase #4	$158.66	12.350%	$178.2545	$178.25	$178.25	$178.30
Purchase #5	$248.40	10.737%	$275.0707	$275.07	$275.05	$275.10
Purchase #6	$30.27	6.159%	$32.1343	$32.13	$32.15	$32.10
Purchase #7	$185.49	5.798%	$196.2447	$196.24	$196.25	$196.20
7 purchase totals =	$1,019.24		$1,123.9072	$1,123.89	$1,123.90	$1,124.00