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	$106.66	10.245%	$117.5873	$117.59	$117.60	$117.60
Purchase #2	$146.92	10.442%	$162.2614	$162.26	$162.25	$162.30
Purchase #3	$72.77	8.181%	$78.7233	$78.72	$78.70	$78.70
Purchase #4	$185.63	10.767%	$205.6168	$205.62	$205.60	$205.60
Purchase #5	$49.71	13.550%	$56.4457	$56.45	$56.45	$56.40
Purchase #6	$123.35	10.750%	$136.6101	$136.61	$136.60	$136.60
Purchase #7	$131.37	9.722%	$144.1418	$144.14	$144.15	$144.10
7 purchase totals =	$816.41		$901.3864	$901.39	$901.35	$901.30