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	$147.32	4.423%	$153.836	$153.84	$153.85	$153.80
Purchase #2	$250.74	11.474%	$279.5099	$279.51	$279.50	$279.50
Purchase #3	$112.83	3.169%	$116.4056	$116.41	$116.40	$116.40
Purchase #4	$164.47	6.419%	$175.0273	$175.03	$175.05	$175.00
Purchase #5	$169.66	9.331%	$185.491	$185.49	$185.50	$185.50
Purchase #6	$205.36	8.798%	$223.4276	$223.43	$223.45	$223.40
Purchase #7	$117.78	13.410%	$133.5743	$133.57	$133.55	$133.60
7 purchase totals =	$1,168.16		$1,267.2717	$1,267.28	$1,267.30	$1,267.20