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	$83.62	12.674%	$94.218	$94.22	$94.20	$94.20
Purchase #2	$134.47	5.537%	$141.9156	$141.92	$141.90	$141.90
Purchase #3	$107.65	6.259%	$114.3878	$114.39	$114.40	$114.40
Purchase #4	$91.52	10.340%	$100.9832	$100.98	$101.00	$101.00
Purchase #5	$111.85	3.861%	$116.1685	$116.17	$116.15	$116.20
Purchase #6	$85.33	5.849%	$90.321	$90.32	$90.30	$90.30
Purchase #7	$118.32	8.338%	$128.1855	$128.19	$128.20	$128.20
7 purchase totals =	$732.76		$786.1796	$786.19	$786.15	$786.20