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	$99.68	7.347%	$107.0035	$107.00	$107.00	$107.00
Purchase #2	$160.59	7.255%	$172.2408	$172.24	$172.25	$172.20
Purchase #3	$120.42	13.351%	$136.4973	$136.50	$136.50	$136.50
Purchase #4	$15.44	12.588%	$17.3836	$17.38	$17.40	$17.40
Purchase #5	$81.47	9.716%	$89.3856	$89.39	$89.40	$89.40
Purchase #6	$190.82	3.250%	$197.0217	$197.02	$197.00	$197.00
Purchase #7	$145.75	4.308%	$152.0289	$152.03	$152.05	$152.00
7 purchase totals =	$814.17		$871.5614	$871.56	$871.60	$871.50