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	$44.90	5.321%	$47.2891	$47.29	$47.30	$47.30
Purchase #2	$229.34	5.233%	$241.3414	$241.34	$241.35	$241.30
Purchase #3	$95.69	9.784%	$105.0523	$105.05	$105.05	$105.10
Purchase #4	$96.82	4.212%	$100.8981	$100.90	$100.90	$100.90
Purchase #5	$169.89	6.209%	$180.4385	$180.44	$180.45	$180.40
Purchase #6	$65.73	6.833%	$70.2213	$70.22	$70.20	$70.20
Purchase #7	$127.81	7.394%	$137.2603	$137.26	$137.25	$137.30
7 purchase totals =	$830.18		$882.5010	$882.50	$882.50	$882.50