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	$211.63	10.233%	$233.2861	$233.29	$233.30	$233.30
Purchase #2	$85.92	3.747%	$89.1394	$89.14	$89.15	$89.10
Purchase #3	$6.27	9.554%	$6.869	$6.87	$6.85	$6.90
Purchase #4	$13.70	8.297%	$14.8367	$14.84	$14.85	$14.80
Purchase #5	$175.70	13.108%	$198.7308	$198.73	$198.75	$198.70
Purchase #6	$64.78	11.748%	$72.3904	$72.39	$72.40	$72.40
Purchase #7	$53.35	6.477%	$56.8055	$56.81	$56.80	$56.80
7 purchase totals =	$611.35		$672.0579	$672.07	$672.10	$672.00