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	$90.56	8.134%	$97.9262	$97.93	$97.95	$97.90
Purchase #2	$83.85	10.703%	$92.8245	$92.82	$92.80	$92.80
Purchase #3	$49.41	5.600%	$52.177	$52.18	$52.20	$52.20
Purchase #4	$96.87	3.285%	$100.0522	$100.05	$100.05	$100.10
Purchase #5	$126.89	8.680%	$137.9041	$137.90	$137.90	$137.90
Purchase #6	$105.32	8.815%	$114.604	$114.60	$114.60	$114.60
Purchase #7	$122.31	5.113%	$128.5637	$128.56	$128.55	$128.60
7 purchase totals =	$675.21		$724.0517	$724.04	$724.05	$724.10