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	$175.83	5.755%	$185.949	$185.95	$185.95	$185.90
Purchase #2	$104.73	11.513%	$116.7876	$116.79	$116.80	$116.80
Purchase #3	$18.55	13.642%	$21.0806	$21.08	$21.10	$21.10
Purchase #4	$241.49	4.204%	$251.6422	$251.64	$251.65	$251.60
Purchase #5	$127.41	3.129%	$131.3967	$131.40	$131.40	$131.40
Purchase #6	$40.38	9.667%	$44.2835	$44.28	$44.30	$44.30
Purchase #7	$36.46	3.792%	$37.8426	$37.84	$37.85	$37.80
7 purchase totals =	$744.85		$788.9822	$788.98	$789.05	$788.90