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	$127.58	3.522%	$132.0734	$132.07	$132.05	$132.10
Purchase #2	$123.32	3.134%	$127.1848	$127.18	$127.20	$127.20
Purchase #3	$26.88	12.548%	$30.2529	$30.25	$30.25	$30.30
Purchase #4	$150.93	4.778%	$158.1414	$158.14	$158.15	$158.10
Purchase #5	$126.68	3.626%	$131.2734	$131.27	$131.25	$131.30
Purchase #6	$156.29	10.154%	$172.1597	$172.16	$172.15	$172.20
Purchase #7	$93.73	10.867%	$103.9156	$103.92	$103.90	$103.90
7 purchase totals =	$805.41		$855.0012	$854.99	$854.95	$855.10