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	$68.42	4.242%	$71.3224	$71.32	$71.30	$71.30
Purchase #2	$214.45	12.584%	$241.4364	$241.44	$241.45	$241.40
Purchase #3	$140.64	7.840%	$151.6662	$151.67	$151.65	$151.70
Purchase #4	$86.43	11.651%	$96.5	$96.50	$96.50	$96.50
Purchase #5	$157.69	9.229%	$172.2432	$172.24	$172.25	$172.20
Purchase #6	$107.74	9.103%	$117.5476	$117.55	$117.55	$117.50
Purchase #7	$200.51	12.219%	$225.0103	$225.01	$225.00	$225.00
7 purchase totals =	$975.88		$1,075.7261	$1,075.73	$1,075.70	$1,075.60