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	$211.94	12.730%	$238.92	$238.92	$238.90	$238.90
Purchase #2	$100.36	6.758%	$107.1423	$107.14	$107.15	$107.10
Purchase #3	$107.79	3.483%	$111.5443	$111.54	$111.55	$111.50
Purchase #4	$142.31	13.387%	$161.361	$161.36	$161.35	$161.40
Purchase #5	$76.85	7.335%	$82.4869	$82.49	$82.50	$82.50
Purchase #6	$98.66	4.677%	$103.2743	$103.27	$103.25	$103.30
Purchase #7	$222.48	12.846%	$251.0598	$251.06	$251.05	$251.10
7 purchase totals =	$960.39		$1,055.7886	$1,055.78	$1,055.75	$1,055.80