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	$195.73	13.717%	$222.5783	$222.58	$222.60	$222.60
Purchase #2	$102.88	10.532%	$113.7153	$113.72	$113.70	$113.70
Purchase #3	$43.42	9.152%	$47.3938	$47.39	$47.40	$47.40
Purchase #4	$10.26	11.396%	$11.4292	$11.43	$11.45	$11.40
Purchase #5	$120.65	9.597%	$132.2288	$132.23	$132.25	$132.20
Purchase #6	$40.97	4.600%	$42.8546	$42.85	$42.85	$42.90
Purchase #7	$185.88	7.327%	$199.4994	$199.50	$199.50	$199.50
7 purchase totals =	$699.79		$769.6994	$769.70	$769.75	$769.70