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	$103.89	5.305%	$109.4014	$109.40	$109.40	$109.40
Purchase #2	$205.66	6.530%	$219.0896	$219.09	$219.10	$219.10
Purchase #3	$84.90	5.859%	$89.8743	$89.87	$89.85	$89.90
Purchase #4	$247.89	13.825%	$282.1608	$282.16	$282.15	$282.20
Purchase #5	$105.91	5.608%	$111.8494	$111.85	$111.85	$111.80
Purchase #6	$61.99	9.866%	$68.1059	$68.11	$68.10	$68.10
Purchase #7	$163.57	6.127%	$173.5919	$173.59	$173.60	$173.60
7 purchase totals =	$973.81		$1,054.0733	$1,054.07	$1,054.05	$1,054.10