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	$48.82	7.415%	$52.44	$52.44	$52.45	$52.40
Purchase #2	$77.88	6.747%	$83.1346	$83.13	$83.15	$83.10
Purchase #3	$185.72	5.277%	$195.5204	$195.52	$195.50	$195.50
Purchase #4	$49.56	4.766%	$51.922	$51.92	$51.90	$51.90
Purchase #5	$103.74	4.369%	$108.2724	$108.27	$108.25	$108.30
Purchase #6	$147.88	8.123%	$159.8923	$159.89	$159.90	$159.90
Purchase #7	$239.88	10.565%	$265.2233	$265.22	$265.20	$265.20
7 purchase totals =	$853.48		$916.4050	$916.39	$916.35	$916.30