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	$211.31	8.618%	$229.5207	$229.52	$229.50	$229.50
Purchase #2	$127.88	12.269%	$143.5696	$143.57	$143.55	$143.60
Purchase #3	$231.66	5.705%	$244.8762	$244.88	$244.90	$244.90
Purchase #4	$13.47	13.623%	$15.305	$15.31	$15.30	$15.30
Purchase #5	$35.70	6.114%	$37.8827	$37.88	$37.90	$37.90
Purchase #6	$106.30	10.586%	$117.5529	$117.55	$117.55	$117.60
Purchase #7	$197.60	4.106%	$205.7135	$205.71	$205.70	$205.70
7 purchase totals =	$923.92		$994.4206	$994.42	$994.40	$994.50