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	$50.64	4.841%	$53.0915	$53.09	$53.10	$53.10
Purchase #2	$165.76	3.464%	$171.5019	$171.50	$171.50	$171.50
Purchase #3	$237.94	7.504%	$255.795	$255.80	$255.80	$255.80
Purchase #4	$129.92	12.613%	$146.3068	$146.31	$146.30	$146.30
Purchase #5	$209.69	9.610%	$229.8412	$229.84	$229.85	$229.80
Purchase #6	$57.65	5.849%	$61.0219	$61.02	$61.00	$61.00
Purchase #7	$20.65	10.177%	$22.7516	$22.75	$22.75	$22.80
7 purchase totals =	$872.25		$940.3099	$940.31	$940.30	$940.30