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	$22.83	11.469%	$25.4484	$25.45	$25.45	$25.40
Purchase #2	$165.68	13.861%	$188.6449	$188.64	$188.65	$188.60
Purchase #3	$49.66	9.269%	$54.263	$54.26	$54.25	$54.30
Purchase #4	$105.90	5.245%	$111.4545	$111.45	$111.45	$111.50
Purchase #5	$103.41	7.656%	$111.3271	$111.33	$111.35	$111.30
Purchase #6	$195.47	4.782%	$204.8174	$204.82	$204.80	$204.80
Purchase #7	$101.75	3.711%	$105.5259	$105.53	$105.55	$105.50
7 purchase totals =	$744.70		$801.4812	$801.48	$801.50	$801.40