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	$126.66	13.570%	$143.8478	$143.85	$143.85	$143.80
Purchase #2	$145.54	8.571%	$158.0142	$158.01	$158.00	$158.00
Purchase #3	$44.43	13.370%	$50.3703	$50.37	$50.35	$50.40
Purchase #4	$172.96	6.197%	$183.6783	$183.68	$183.70	$183.70
Purchase #5	$50.53	7.413%	$54.2758	$54.28	$54.30	$54.30
Purchase #6	$27.42	7.275%	$29.4148	$29.41	$29.40	$29.40
Purchase #7	$33.35	13.271%	$37.7759	$37.78	$37.80	$37.80
7 purchase totals =	$600.89		$657.3771	$657.38	$657.40	$657.40