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	$101.58	10.669%	$112.4176	$112.42	$112.40	$112.40
Purchase #2	$37.99	13.304%	$43.0442	$43.04	$43.05	$43.00
Purchase #3	$79.75	11.415%	$88.8535	$88.85	$88.85	$88.90
Purchase #4	$41.82	6.626%	$44.591	$44.59	$44.60	$44.60
Purchase #5	$178.91	4.468%	$186.9037	$186.90	$186.90	$186.90
Purchase #6	$33.54	12.298%	$37.6647	$37.66	$37.65	$37.70
Purchase #7	$208.32	7.376%	$223.6857	$223.69	$223.70	$223.70
7 purchase totals =	$681.91		$737.1604	$737.15	$737.15	$737.20