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	$189.55	8.527%	$205.7129	$205.71	$205.70	$205.70
Purchase #2	$72.26	11.244%	$80.3849	$80.38	$80.40	$80.40
Purchase #3	$78.43	12.830%	$88.4926	$88.49	$88.50	$88.50
Purchase #4	$138.78	5.590%	$146.5378	$146.54	$146.55	$146.50
Purchase #5	$242.58	9.768%	$266.2752	$266.28	$266.30	$266.30
Purchase #6	$123.53	3.496%	$127.8486	$127.85	$127.85	$127.80
Purchase #7	$216.58	9.550%	$237.2634	$237.26	$237.25	$237.30
7 purchase totals =	$1,061.71		$1,152.5154	$1,152.51	$1,152.55	$1,152.50