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	$46.58	8.688%	$50.6269	$50.63	$50.65	$50.60
Purchase #2	$145.47	6.848%	$155.4318	$155.43	$155.45	$155.40
Purchase #3	$216.42	12.811%	$244.1456	$244.15	$244.15	$244.10
Purchase #4	$112.42	13.661%	$127.7777	$127.78	$127.80	$127.80
Purchase #5	$145.65	5.129%	$153.1204	$153.12	$153.10	$153.10
Purchase #6	$161.59	6.214%	$171.6312	$171.63	$171.65	$171.60
Purchase #7	$101.76	12.692%	$114.6754	$114.68	$114.70	$114.70
7 purchase totals =	$929.89		$1,017.4090	$1,017.42	$1,017.50	$1,017.30