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	$106.95	4.427%	$111.6847	$111.68	$111.70	$111.70
Purchase #2	$231.91	13.622%	$263.5008	$263.50	$263.50	$263.50
Purchase #3	$37.45	6.807%	$39.9992	$40.00	$40.00	$40.00
Purchase #4	$32.96	12.409%	$37.05	$37.05	$37.05	$37.10
Purchase #5	$159.68	7.761%	$172.0728	$172.07	$172.05	$172.10
Purchase #6	$76.51	9.749%	$83.969	$83.97	$83.95	$84.00
Purchase #7	$138.51	13.283%	$156.9083	$156.91	$156.90	$156.90
7 purchase totals =	$783.97		$865.1848	$865.18	$865.15	$865.30