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	$65.65	3.677%	$68.064	$68.06	$68.05	$68.10
Purchase #2	$167.89	6.287%	$178.4452	$178.45	$178.45	$178.40
Purchase #3	$41.26	3.205%	$42.5824	$42.58	$42.60	$42.60
Purchase #4	$158.82	13.297%	$179.9383	$179.94	$179.95	$179.90
Purchase #5	$101.73	6.620%	$108.4645	$108.46	$108.45	$108.50
Purchase #6	$250.72	4.681%	$262.4562	$262.46	$262.45	$262.50
Purchase #7	$95.87	9.831%	$105.295	$105.30	$105.30	$105.30
7 purchase totals =	$881.94		$945.2456	$945.25	$945.25	$945.30