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	$196.38	13.191%	$222.2845	$222.28	$222.30	$222.30
Purchase #2	$34.87	4.315%	$36.3746	$36.37	$36.35	$36.40
Purchase #3	$83.52	9.703%	$91.6239	$91.62	$91.60	$91.60
Purchase #4	$139.66	12.366%	$156.9304	$156.93	$156.95	$156.90
Purchase #5	$76.43	3.187%	$78.8658	$78.87	$78.85	$78.90
Purchase #6	$5.72	11.299%	$6.3663	$6.37	$6.35	$6.40
Purchase #7	$19.62	4.255%	$20.4548	$20.45	$20.45	$20.50
7 purchase totals =	$556.20		$612.9003	$612.89	$612.85	$613.00