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	$179.59	11.167%	$199.6448	$199.64	$199.65	$199.60
Purchase #2	$229.73	6.297%	$244.1961	$244.20	$244.20	$244.20
Purchase #3	$96.81	13.123%	$109.5144	$109.51	$109.50	$109.50
Purchase #4	$239.31	13.666%	$272.0141	$272.01	$272.00	$272.00
Purchase #5	$175.83	4.550%	$183.8303	$183.83	$183.85	$183.80
Purchase #6	$172.74	13.819%	$196.6109	$196.61	$196.60	$196.60
Purchase #7	$245.38	8.531%	$266.3134	$266.31	$266.30	$266.30
7 purchase totals =	$1,339.39		$1,472.1240	$1,472.11	$1,472.10	$1,472.00