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	$188.48	13.602%	$214.117	$214.12	$214.10	$214.10
Purchase #2	$216.40	12.423%	$243.2834	$243.28	$243.30	$243.30
Purchase #3	$11.54	12.869%	$13.0251	$13.03	$13.05	$13.00
Purchase #4	$11.83	5.670%	$12.5008	$12.50	$12.50	$12.50
Purchase #5	$225.27	5.594%	$237.8716	$237.87	$237.85	$237.90
Purchase #6	$113.35	12.513%	$127.5335	$127.53	$127.55	$127.50
Purchase #7	$213.52	9.563%	$233.9389	$233.94	$233.95	$233.90
7 purchase totals =	$980.39		$1,082.2703	$1,082.27	$1,082.30	$1,082.20