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	$30.87	8.181%	$33.3955	$33.40	$33.40	$33.40
Purchase #2	$24.81	3.508%	$25.6803	$25.68	$25.70	$25.70
Purchase #3	$170.98	11.874%	$191.2822	$191.28	$191.30	$191.30
Purchase #4	$111.74	4.409%	$116.6666	$116.67	$116.65	$116.70
Purchase #5	$38.38	12.427%	$43.1495	$43.15	$43.15	$43.10
Purchase #6	$228.71	4.433%	$238.8487	$238.85	$238.85	$238.80
Purchase #7	$108.59	9.157%	$118.5336	$118.53	$118.55	$118.50
7 purchase totals =	$714.08		$767.5564	$767.56	$767.60	$767.50