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	$184.77	6.120%	$196.0779	$196.08	$196.10	$196.10
Purchase #2	$16.50	4.440%	$17.2326	$17.23	$17.25	$17.20
Purchase #3	$108.81	13.477%	$123.4743	$123.47	$123.45	$123.50
Purchase #4	$131.52	4.536%	$137.4857	$137.49	$137.50	$137.50
Purchase #5	$46.69	8.313%	$50.5713	$50.57	$50.55	$50.60
Purchase #6	$47.94	10.816%	$53.1252	$53.13	$53.15	$53.10
Purchase #7	$199.68	11.817%	$223.2762	$223.28	$223.30	$223.30
7 purchase totals =	$735.91		$801.2432	$801.25	$801.30	$801.30