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	$91.52	3.305%	$94.5447	$94.54	$94.55	$94.50
Purchase #2	$53.36	5.324%	$56.2009	$56.20	$56.20	$56.20
Purchase #3	$58.27	12.656%	$65.6447	$65.64	$65.65	$65.60
Purchase #4	$71.45	4.659%	$74.7789	$74.78	$74.80	$74.80
Purchase #5	$107.34	12.262%	$120.502	$120.50	$120.50	$120.50
Purchase #6	$112.93	12.867%	$127.4607	$127.46	$127.45	$127.50
Purchase #7	$141.52	6.295%	$150.4287	$150.43	$150.45	$150.40
7 purchase totals =	$636.39		$689.5606	$689.55	$689.60	$689.50