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	$167.35	13.811%	$190.4627	$190.46	$190.45	$190.50
Purchase #2	$211.28	6.863%	$225.7801	$225.78	$225.80	$225.80
Purchase #3	$210.26	13.461%	$238.5631	$238.56	$238.55	$238.60
Purchase #4	$51.84	9.150%	$56.5834	$56.58	$56.60	$56.60
Purchase #5	$247.95	7.389%	$266.271	$266.27	$266.25	$266.30
Purchase #6	$143.48	13.128%	$162.3161	$162.32	$162.30	$162.30
Purchase #7	$210.83	10.577%	$233.1295	$233.13	$233.15	$233.10
7 purchase totals =	$1,242.99		$1,373.1059	$1,373.10	$1,373.10	$1,373.20