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	$137.47	10.529%	$151.9442	$151.94	$151.95	$151.90
Purchase #2	$88.39	4.326%	$92.2138	$92.21	$92.20	$92.20
Purchase #3	$163.60	8.147%	$176.9285	$176.93	$176.95	$176.90
Purchase #4	$91.84	12.485%	$103.3062	$103.31	$103.30	$103.30
Purchase #5	$249.62	9.270%	$272.7598	$272.76	$272.75	$272.80
Purchase #6	$72.98	7.790%	$78.6651	$78.67	$78.65	$78.70
Purchase #7	$111.77	13.358%	$126.7002	$126.70	$126.70	$126.70
7 purchase totals =	$915.67		$1,002.5178	$1,002.52	$1,002.50	$1,002.50