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	$92.71	13.479%	$105.2064	$105.21	$105.20	$105.20
Purchase #2	$140.45	9.339%	$153.5666	$153.57	$153.55	$153.60
Purchase #3	$106.79	4.185%	$111.2592	$111.26	$111.25	$111.30
Purchase #4	$161.33	6.724%	$172.1778	$172.18	$172.20	$172.20
Purchase #5	$26.44	6.839%	$28.2482	$28.25	$28.25	$28.20
Purchase #6	$110.47	11.494%	$123.1674	$123.17	$123.15	$123.20
Purchase #7	$33.29	11.734%	$37.1962	$37.20	$37.20	$37.20
7 purchase totals =	$671.48		$730.8218	$730.84	$730.80	$730.90