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	$190.95	8.168%	$206.5468	$206.55	$206.55	$206.50
Purchase #2	$102.67	9.634%	$112.5612	$112.56	$112.55	$112.60
Purchase #3	$247.87	10.298%	$273.3957	$273.40	$273.40	$273.40
Purchase #4	$153.38	5.785%	$162.253	$162.25	$162.25	$162.30
Purchase #5	$216.26	10.477%	$238.9176	$238.92	$238.90	$238.90
Purchase #6	$99.62	12.150%	$111.7238	$111.72	$111.70	$111.70
Purchase #7	$172.42	10.255%	$190.1017	$190.10	$190.10	$190.10
7 purchase totals =	$1,183.17		$1,295.4998	$1,295.50	$1,295.45	$1,295.50