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	$181.52	12.830%	$204.809	$204.81	$204.80	$204.80
Purchase #2	$153.69	7.346%	$164.9801	$164.98	$165.00	$165.00
Purchase #3	$194.79	6.397%	$207.2507	$207.25	$207.25	$207.30
Purchase #4	$53.30	11.540%	$59.4508	$59.45	$59.45	$59.50
Purchase #5	$122.98	3.548%	$127.3433	$127.34	$127.35	$127.30
Purchase #6	$117.42	13.531%	$133.3081	$133.31	$133.30	$133.30
Purchase #7	$119.25	5.761%	$126.12	$126.12	$126.10	$126.10
7 purchase totals =	$942.95		$1,023.2620	$1,023.26	$1,023.25	$1,023.30