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	$99.47	10.141%	$109.5573	$109.56	$109.55	$109.60
Purchase #2	$165.83	9.717%	$181.9437	$181.94	$181.95	$181.90
Purchase #3	$229.42	11.781%	$256.448	$256.45	$256.45	$256.40
Purchase #4	$38.51	5.106%	$40.4763	$40.48	$40.50	$40.50
Purchase #5	$241.91	8.461%	$262.378	$262.38	$262.40	$262.40
Purchase #6	$182.49	9.743%	$200.27	$200.27	$200.25	$200.30
Purchase #7	$159.72	8.411%	$173.154	$173.15	$173.15	$173.20
7 purchase totals =	$1,117.35		$1,224.2273	$1,224.23	$1,224.25	$1,224.30