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	$173.94	9.575%	$190.5948	$190.59	$190.60	$190.60
Purchase #2	$152.66	10.771%	$169.103	$169.10	$169.10	$169.10
Purchase #3	$168.64	7.411%	$181.1379	$181.14	$181.15	$181.10
Purchase #4	$152.74	13.184%	$172.8772	$172.88	$172.90	$172.90
Purchase #5	$47.30	11.505%	$52.7419	$52.74	$52.75	$52.70
Purchase #6	$44.91	3.198%	$46.3462	$46.35	$46.35	$46.30
Purchase #7	$145.59	8.642%	$158.1719	$158.17	$158.15	$158.20
7 purchase totals =	$885.78		$970.9729	$970.97	$971.00	$970.90