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	$232.80	13.597%	$264.4538	$264.45	$264.45	$264.50
Purchase #2	$72.32	7.453%	$77.71	$77.71	$77.70	$77.70
Purchase #3	$65.92	10.489%	$72.8343	$72.83	$72.85	$72.80
Purchase #4	$106.64	13.653%	$121.1996	$121.20	$121.20	$121.20
Purchase #5	$62.38	7.330%	$66.9525	$66.95	$66.95	$67.00
Purchase #6	$74.56	4.721%	$78.08	$78.08	$78.10	$78.10
Purchase #7	$77.96	5.693%	$82.3983	$82.40	$82.40	$82.40
7 purchase totals =	$692.58		$763.6285	$763.62	$763.65	$763.70