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	$171.55	4.849%	$179.8685	$179.87	$179.85	$179.90
Purchase #2	$165.43	5.117%	$173.8951	$173.90	$173.90	$173.90
Purchase #3	$185.37	6.154%	$196.7777	$196.78	$196.80	$196.80
Purchase #4	$110.91	10.690%	$122.7663	$122.77	$122.75	$122.80
Purchase #5	$103.64	5.572%	$109.4148	$109.41	$109.40	$109.40
Purchase #6	$105.39	5.649%	$111.3435	$111.34	$111.35	$111.30
Purchase #7	$54.74	5.694%	$57.8569	$57.86	$57.85	$57.90
7 purchase totals =	$897.03		$951.9228	$951.93	$951.90	$952.00