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	$82.54	13.374%	$93.5789	$93.58	$93.60	$93.60
Purchase #2	$25.96	6.491%	$27.6451	$27.65	$27.65	$27.60
Purchase #3	$49.82	6.396%	$53.0065	$53.01	$53.00	$53.00
Purchase #4	$98.98	12.693%	$111.5435	$111.54	$111.55	$111.50
Purchase #5	$118.42	5.226%	$124.6086	$124.61	$124.60	$124.60
Purchase #6	$230.76	9.784%	$253.3376	$253.34	$253.35	$253.30
Purchase #7	$41.51	8.603%	$45.0811	$45.08	$45.10	$45.10
7 purchase totals =	$647.99		$708.8013	$708.81	$708.85	$708.70