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	$185.70	7.431%	$199.4994	$199.50	$199.50	$199.50
Purchase #2	$215.61	13.363%	$244.422	$244.42	$244.40	$244.40
Purchase #3	$5.55	13.325%	$6.2895	$6.29	$6.30	$6.30
Purchase #4	$48.28	11.621%	$53.8906	$53.89	$53.90	$53.90
Purchase #5	$246.35	10.590%	$272.4385	$272.44	$272.45	$272.40
Purchase #6	$54.80	4.196%	$57.0994	$57.10	$57.10	$57.10
Purchase #7	$114.53	8.139%	$123.8516	$123.85	$123.85	$123.90
7 purchase totals =	$870.82		$957.4910	$957.49	$957.50	$957.50