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	$238.37	3.327%	$246.3006	$246.30	$246.30	$246.30
Purchase #2	$5.48	9.194%	$5.9838	$5.98	$6.00	$6.00
Purchase #3	$100.74	4.821%	$105.5967	$105.60	$105.60	$105.60
Purchase #4	$9.77	9.796%	$10.7271	$10.73	$10.75	$10.70
Purchase #5	$227.37	8.849%	$247.49	$247.49	$247.50	$247.50
Purchase #6	$37.87	11.475%	$42.2156	$42.22	$42.20	$42.20
Purchase #7	$101.41	9.626%	$111.1717	$111.17	$111.15	$111.20
7 purchase totals =	$721.01		$769.4855	$769.49	$769.50	$769.50