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	$157.31	9.621%	$172.4448	$172.44	$172.45	$172.40
Purchase #2	$28.61	11.518%	$31.9053	$31.91	$31.90	$31.90
Purchase #3	$140.54	10.723%	$155.6101	$155.61	$155.60	$155.60
Purchase #4	$131.75	10.692%	$145.8367	$145.84	$145.85	$145.80
Purchase #5	$239.84	9.327%	$262.2099	$262.21	$262.20	$262.20
Purchase #6	$133.99	13.573%	$152.1765	$152.18	$152.20	$152.20
Purchase #7	$137.30	5.691%	$145.1137	$145.11	$145.10	$145.10
7 purchase totals =	$969.34		$1,065.2970	$1,065.30	$1,065.30	$1,065.20