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	$98.67	12.753%	$111.2534	$111.25	$111.25	$111.30
Purchase #2	$96.60	7.313%	$103.6644	$103.66	$103.65	$103.70
Purchase #3	$204.39	8.713%	$222.1985	$222.20	$222.20	$222.20
Purchase #4	$243.25	4.867%	$255.089	$255.09	$255.10	$255.10
Purchase #5	$143.57	3.495%	$148.5878	$148.59	$148.60	$148.60
Purchase #6	$90.98	11.428%	$101.3772	$101.38	$101.40	$101.40
Purchase #7	$118.55	6.608%	$126.3838	$126.38	$126.40	$126.40
7 purchase totals =	$996.01		$1,068.5541	$1,068.55	$1,068.60	$1,068.70