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	$103.66	7.694%	$111.6356	$111.64	$111.65	$111.60
Purchase #2	$249.73	11.512%	$278.4789	$278.48	$278.50	$278.50
Purchase #3	$60.76	4.818%	$63.6874	$63.69	$63.70	$63.70
Purchase #4	$229.42	12.663%	$258.4715	$258.47	$258.45	$258.50
Purchase #5	$250.45	5.299%	$263.7213	$263.72	$263.70	$263.70
Purchase #6	$12.78	11.448%	$14.2431	$14.24	$14.25	$14.20
Purchase #7	$100.49	3.516%	$104.0232	$104.02	$104.00	$104.00
7 purchase totals =	$1,007.29		$1,094.2610	$1,094.26	$1,094.25	$1,094.20