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	$98.64	10.499%	$108.9962	$109.00	$109.00	$109.00
Purchase #2	$138.59	5.399%	$146.0725	$146.07	$146.05	$146.10
Purchase #3	$44.37	6.151%	$47.0992	$47.10	$47.10	$47.10
Purchase #4	$112.34	4.565%	$117.4683	$117.47	$117.45	$117.50
Purchase #5	$178.38	6.550%	$190.0639	$190.06	$190.05	$190.10
Purchase #6	$118.32	7.338%	$127.0023	$127.00	$127.00	$127.00
Purchase #7	$150.28	6.368%	$159.8498	$159.85	$159.85	$159.80
7 purchase totals =	$840.92		$896.5522	$896.55	$896.50	$896.60