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	$145.41	4.209%	$151.5303	$151.53	$151.55	$151.50
Purchase #2	$188.95	11.683%	$211.025	$211.03	$211.05	$211.00
Purchase #3	$191.56	7.689%	$206.289	$206.29	$206.30	$206.30
Purchase #4	$71.42	4.269%	$74.4689	$74.47	$74.45	$74.50
Purchase #5	$79.55	12.105%	$89.1795	$89.18	$89.20	$89.20
Purchase #6	$95.32	12.857%	$107.5753	$107.58	$107.60	$107.60
Purchase #7	$92.89	11.273%	$103.3615	$103.36	$103.35	$103.40
7 purchase totals =	$865.10		$943.4295	$943.44	$943.50	$943.50