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	$91.84	12.784%	$103.5808	$103.58	$103.60	$103.60
Purchase #2	$176.42	13.721%	$200.6266	$200.63	$200.65	$200.60
Purchase #3	$226.70	5.219%	$238.5315	$238.53	$238.55	$238.50
Purchase #4	$208.94	3.145%	$215.5112	$215.51	$215.50	$215.50
Purchase #5	$50.91	11.430%	$56.729	$56.73	$56.75	$56.70
Purchase #6	$219.63	8.123%	$237.4705	$237.47	$237.45	$237.50
Purchase #7	$111.98	9.680%	$122.8197	$122.82	$122.80	$122.80
7 purchase totals =	$1,086.42		$1,175.2693	$1,175.27	$1,175.30	$1,175.20