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	$104.98	3.396%	$108.5451	$108.55	$108.55	$108.50
Purchase #2	$29.83	12.401%	$33.5292	$33.53	$33.55	$33.50
Purchase #3	$116.52	9.608%	$127.7152	$127.72	$127.70	$127.70
Purchase #4	$111.72	13.230%	$126.5006	$126.50	$126.50	$126.50
Purchase #5	$146.86	13.287%	$166.3733	$166.37	$166.35	$166.40
Purchase #6	$122.28	5.462%	$128.9589	$128.96	$128.95	$129.00
Purchase #7	$24.46	4.858%	$25.6483	$25.65	$25.65	$25.60
7 purchase totals =	$656.65		$717.2706	$717.28	$717.25	$717.20