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	$109.85	7.279%	$117.846	$117.85	$117.85	$117.80
Purchase #2	$211.72	13.171%	$239.6056	$239.61	$239.60	$239.60
Purchase #3	$153.94	3.461%	$159.2679	$159.27	$159.25	$159.30
Purchase #4	$199.45	8.737%	$216.8759	$216.88	$216.90	$216.90
Purchase #5	$166.68	8.766%	$181.2912	$181.29	$181.30	$181.30
Purchase #6	$35.51	13.852%	$40.4288	$40.43	$40.45	$40.40
Purchase #7	$180.52	5.299%	$190.0858	$190.09	$190.10	$190.10
7 purchase totals =	$1,057.67		$1,145.4012	$1,145.42	$1,145.45	$1,145.40