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	$134.86	6.784%	$144.0089	$144.01	$144.00	$144.00
Purchase #2	$11.41	9.197%	$12.4594	$12.46	$12.45	$12.50
Purchase #3	$49.62	9.802%	$54.4838	$54.48	$54.50	$54.50
Purchase #4	$40.75	3.373%	$42.1245	$42.12	$42.10	$42.10
Purchase #5	$155.26	6.798%	$165.8146	$165.81	$165.80	$165.80
Purchase #6	$26.58	12.505%	$29.9038	$29.90	$29.90	$29.90
Purchase #7	$100.51	8.819%	$109.374	$109.37	$109.35	$109.40
7 purchase totals =	$518.99		$558.1690	$558.15	$558.10	$558.20