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	$118.44	10.170%	$130.4853	$130.49	$130.50	$130.50
Purchase #2	$146.83	12.633%	$165.379	$165.38	$165.40	$165.40
Purchase #3	$152.94	12.750%	$172.4399	$172.44	$172.45	$172.40
Purchase #4	$106.60	11.247%	$118.5893	$118.59	$118.60	$118.60
Purchase #5	$250.75	6.575%	$267.2368	$267.24	$267.25	$267.20
Purchase #6	$199.30	8.490%	$216.2206	$216.22	$216.20	$216.20
Purchase #7	$210.45	9.466%	$230.3712	$230.37	$230.35	$230.40
7 purchase totals =	$1,185.31		$1,300.7221	$1,300.73	$1,300.75	$1,300.70