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	$107.32	8.360%	$116.292	$116.29	$116.30	$116.30
Purchase #2	$121.56	8.615%	$132.0324	$132.03	$132.05	$132.00
Purchase #3	$151.64	13.683%	$172.3889	$172.39	$172.40	$172.40
Purchase #4	$122.73	3.830%	$127.4306	$127.43	$127.45	$127.40
Purchase #5	$244.51	7.672%	$263.2688	$263.27	$263.25	$263.30
Purchase #6	$126.36	4.779%	$132.3987	$132.40	$132.40	$132.40
Purchase #7	$242.32	6.110%	$257.1258	$257.13	$257.15	$257.10
7 purchase totals =	$1,116.44		$1,200.9372	$1,200.94	$1,201.00	$1,200.90