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	$30.82	11.780%	$34.4506	$34.45	$34.45	$34.50
Purchase #2	$236.27	10.258%	$260.5066	$260.51	$260.50	$260.50
Purchase #3	$124.61	13.629%	$141.5931	$141.59	$141.60	$141.60
Purchase #4	$173.94	11.289%	$193.5761	$193.58	$193.60	$193.60
Purchase #5	$217.40	10.665%	$240.5857	$240.59	$240.60	$240.60
Purchase #6	$181.51	5.401%	$191.3134	$191.31	$191.30	$191.30
Purchase #7	$107.98	3.647%	$111.918	$111.92	$111.90	$111.90
7 purchase totals =	$1,072.53		$1,173.9435	$1,173.95	$1,173.95	$1,174.00