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	$106.87	4.742%	$111.9378	$111.94	$111.95	$111.90
Purchase #2	$62.41	7.323%	$66.9803	$66.98	$67.00	$67.00
Purchase #3	$217.88	10.213%	$240.1321	$240.13	$240.15	$240.10
Purchase #4	$116.27	6.484%	$123.8089	$123.81	$123.80	$123.80
Purchase #5	$56.28	3.106%	$58.0281	$58.03	$58.05	$58.00
Purchase #6	$158.49	9.508%	$173.5592	$173.56	$173.55	$173.60
Purchase #7	$119.46	12.855%	$134.8166	$134.82	$134.80	$134.80
7 purchase totals =	$837.66		$909.2630	$909.27	$909.30	$909.20