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	$95.28	6.747%	$101.7085	$101.71	$101.70	$101.70
Purchase #2	$158.75	8.731%	$172.6105	$172.61	$172.60	$172.60
Purchase #3	$126.52	13.300%	$143.3472	$143.35	$143.35	$143.30
Purchase #4	$179.84	4.543%	$188.0101	$188.01	$188.00	$188.00
Purchase #5	$65.81	7.554%	$70.7813	$70.78	$70.80	$70.80
Purchase #6	$98.87	12.599%	$111.3266	$111.33	$111.35	$111.30
Purchase #7	$216.87	7.856%	$233.9073	$233.91	$233.90	$233.90
7 purchase totals =	$941.94		$1,021.6915	$1,021.70	$1,021.70	$1,021.60