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	$233.72	5.698%	$247.0374	$247.04	$247.05	$247.00
Purchase #2	$123.74	3.213%	$127.7158	$127.72	$127.70	$127.70
Purchase #3	$103.99	5.341%	$109.5441	$109.54	$109.55	$109.50
Purchase #4	$154.80	6.289%	$164.5354	$164.54	$164.55	$164.50
Purchase #5	$244.47	11.607%	$272.8456	$272.85	$272.85	$272.80
Purchase #6	$111.75	4.755%	$117.0637	$117.06	$117.05	$117.10
Purchase #7	$249.87	5.686%	$264.0776	$264.08	$264.10	$264.10
7 purchase totals =	$1,222.34		$1,302.8196	$1,302.83	$1,302.85	$1,302.70