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	$40.30	13.102%	$45.5801	$45.58	$45.60	$45.60
Purchase #2	$184.80	4.565%	$193.2361	$193.24	$193.25	$193.20
Purchase #3	$103.62	9.273%	$113.2287	$113.23	$113.25	$113.20
Purchase #4	$124.66	6.243%	$132.4425	$132.44	$132.45	$132.40
Purchase #5	$214.95	3.565%	$222.613	$222.61	$222.60	$222.60
Purchase #6	$48.70	4.518%	$50.9003	$50.90	$50.90	$50.90
Purchase #7	$80.62	11.472%	$89.8687	$89.87	$89.85	$89.90
7 purchase totals =	$797.65		$847.8694	$847.87	$847.90	$847.80