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	$211.44	12.596%	$238.073	$238.07	$238.05	$238.10
Purchase #2	$42.52	8.723%	$46.229	$46.23	$46.25	$46.20
Purchase #3	$241.39	7.247%	$258.8835	$258.88	$258.90	$258.90
Purchase #4	$59.90	3.290%	$61.8707	$61.87	$61.85	$61.90
Purchase #5	$221.61	13.612%	$251.7756	$251.78	$251.80	$251.80
Purchase #6	$50.50	12.262%	$56.6923	$56.69	$56.70	$56.70
Purchase #7	$129.66	11.570%	$144.6617	$144.66	$144.65	$144.70
7 purchase totals =	$957.02		$1,058.1858	$1,058.18	$1,058.20	$1,058.30