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	$130.64	11.848%	$146.1182	$146.12	$146.10	$146.10
Purchase #2	$189.40	7.703%	$203.9895	$203.99	$204.00	$204.00
Purchase #3	$46.32	9.805%	$50.8617	$50.86	$50.85	$50.90
Purchase #4	$138.72	3.865%	$144.0815	$144.08	$144.10	$144.10
Purchase #5	$100.27	11.303%	$111.6035	$111.60	$111.60	$111.60
Purchase #6	$217.49	10.837%	$241.0594	$241.06	$241.05	$241.10
Purchase #7	$76.38	7.760%	$82.3071	$82.31	$82.30	$82.30
7 purchase totals =	$899.22		$980.0209	$980.02	$980.00	$980.10