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	$102.69	8.500%	$111.4187	$111.42	$111.40	$111.40
Purchase #2	$219.95	8.312%	$238.2322	$238.23	$238.25	$238.20
Purchase #3	$213.85	7.385%	$229.6428	$229.64	$229.65	$229.60
Purchase #4	$37.25	8.599%	$40.4531	$40.45	$40.45	$40.50
Purchase #5	$138.79	13.231%	$157.1533	$157.15	$157.15	$157.20
Purchase #6	$102.70	8.247%	$111.1697	$111.17	$111.15	$111.20
Purchase #7	$158.35	6.428%	$168.5287	$168.53	$168.55	$168.50
7 purchase totals =	$973.58		$1,056.5985	$1,056.59	$1,056.60	$1,056.60