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	$107.42	6.567%	$114.4743	$114.47	$114.45	$114.50
Purchase #2	$99.32	12.202%	$111.439	$111.44	$111.45	$111.40
Purchase #3	$27.94	12.579%	$31.4546	$31.45	$31.45	$31.50
Purchase #4	$46.56	9.784%	$51.1154	$51.12	$51.10	$51.10
Purchase #5	$222.49	11.292%	$247.6136	$247.61	$247.60	$247.60
Purchase #6	$233.32	10.399%	$257.5829	$257.58	$257.60	$257.60
Purchase #7	$221.50	13.485%	$251.3693	$251.37	$251.35	$251.40
7 purchase totals =	$958.55		$1,065.0491	$1,065.04	$1,065.00	$1,065.10