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	$176.40	7.391%	$189.4377	$189.44	$189.45	$189.40
Purchase #2	$153.44	13.593%	$174.2971	$174.30	$174.30	$174.30
Purchase #3	$139.83	4.532%	$146.1671	$146.17	$146.15	$146.20
Purchase #4	$38.39	9.397%	$41.9975	$42.00	$42.00	$42.00
Purchase #5	$104.32	10.120%	$114.8772	$114.88	$114.90	$114.90
Purchase #6	$86.35	3.145%	$89.0657	$89.07	$89.05	$89.10
Purchase #7	$105.98	10.252%	$116.8451	$116.85	$116.85	$116.80
7 purchase totals =	$804.71		$872.6874	$872.71	$872.70	$872.70