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	$76.51	13.414%	$86.7731	$86.77	$86.75	$86.80
Purchase #2	$184.94	3.748%	$191.8716	$191.87	$191.85	$191.90
Purchase #3	$22.85	13.470%	$25.9279	$25.93	$25.95	$25.90
Purchase #4	$197.75	9.853%	$217.2343	$217.23	$217.25	$217.20
Purchase #5	$169.28	5.818%	$179.1287	$179.13	$179.15	$179.10
Purchase #6	$65.83	13.183%	$74.5084	$74.51	$74.50	$74.50
Purchase #7	$103.42	7.419%	$111.0927	$111.09	$111.10	$111.10
7 purchase totals =	$820.58		$886.5367	$886.53	$886.55	$886.50