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	$153.88	3.128%	$158.6934	$158.69	$158.70	$158.70
Purchase #2	$209.80	13.513%	$238.1503	$238.15	$238.15	$238.20
Purchase #3	$41.44	4.683%	$43.3806	$43.38	$43.40	$43.40
Purchase #4	$35.81	5.176%	$37.6635	$37.66	$37.65	$37.70
Purchase #5	$25.53	8.444%	$27.6858	$27.69	$27.70	$27.70
Purchase #6	$108.91	5.169%	$114.5396	$114.54	$114.55	$114.50
Purchase #7	$129.59	7.778%	$139.6695	$139.67	$139.65	$139.70
7 purchase totals =	$704.96		$759.7827	$759.78	$759.80	$759.90