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	$217.53	9.778%	$238.8001	$238.80	$238.80	$238.80
Purchase #2	$206.41	6.164%	$219.1331	$219.13	$219.15	$219.10
Purchase #3	$95.95	4.771%	$100.5278	$100.53	$100.55	$100.50
Purchase #4	$245.53	4.439%	$256.4291	$256.43	$256.45	$256.40
Purchase #5	$243.32	10.180%	$268.09	$268.09	$268.10	$268.10
Purchase #6	$172.63	7.652%	$185.8396	$185.84	$185.85	$185.80
Purchase #7	$146.91	12.706%	$165.5764	$165.58	$165.60	$165.60
7 purchase totals =	$1,328.28		$1,434.3961	$1,434.40	$1,434.50	$1,434.30