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	$172.63	5.219%	$181.6396	$181.64	$181.65	$181.60
Purchase #2	$20.37	12.271%	$22.8696	$22.87	$22.85	$22.90
Purchase #3	$132.89	9.544%	$145.573	$145.57	$145.55	$145.60
Purchase #4	$105.35	5.423%	$111.0631	$111.06	$111.05	$111.10
Purchase #5	$100.35	10.200%	$110.5857	$110.59	$110.60	$110.60
Purchase #6	$61.61	9.201%	$67.2787	$67.28	$67.30	$67.30
Purchase #7	$94.72	6.612%	$100.9829	$100.98	$101.00	$101.00
7 purchase totals =	$687.92		$739.9926	$739.99	$740.00	$740.10