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	$68.42	12.504%	$76.9752	$76.98	$77.00	$77.00
Purchase #2	$100.77	12.229%	$113.0932	$113.09	$113.10	$113.10
Purchase #3	$172.77	10.173%	$190.3459	$190.35	$190.35	$190.30
Purchase #4	$33.69	3.571%	$34.8931	$34.89	$34.90	$34.90
Purchase #5	$94.42	12.332%	$106.0639	$106.06	$106.05	$106.10
Purchase #6	$169.92	6.103%	$180.2902	$180.29	$180.30	$180.30
Purchase #7	$202.43	10.540%	$223.7661	$223.77	$223.75	$223.80
7 purchase totals =	$842.42		$925.4276	$925.43	$925.45	$925.50