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	$250.82	12.685%	$282.6365	$282.64	$282.65	$282.60
Purchase #2	$212.72	8.435%	$230.6629	$230.66	$230.65	$230.70
Purchase #3	$95.91	3.716%	$99.474	$99.47	$99.45	$99.50
Purchase #4	$134.57	6.330%	$143.0883	$143.09	$143.10	$143.10
Purchase #5	$94.91	12.615%	$106.8829	$106.88	$106.90	$106.90
Purchase #6	$144.68	12.141%	$162.2456	$162.25	$162.25	$162.20
Purchase #7	$35.39	11.365%	$39.4121	$39.41	$39.40	$39.40
7 purchase totals =	$969.00		$1,064.4023	$1,064.40	$1,064.40	$1,064.40