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	$96.78	3.262%	$99.937	$99.94	$99.95	$99.90
Purchase #2	$50.56	10.843%	$56.0422	$56.04	$56.05	$56.00
Purchase #3	$51.80	3.314%	$53.5167	$53.52	$53.50	$53.50
Purchase #4	$72.82	3.582%	$75.4284	$75.43	$75.45	$75.40
Purchase #5	$147.67	5.107%	$155.2115	$155.21	$155.20	$155.20
Purchase #6	$72.53	3.255%	$74.8909	$74.89	$74.90	$74.90
Purchase #7	$207.60	4.684%	$217.324	$217.32	$217.30	$217.30
7 purchase totals =	$699.76		$732.3507	$732.35	$732.35	$732.20