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	$141.94	8.114%	$153.457	$153.46	$153.45	$153.50
Purchase #2	$163.69	12.542%	$184.22	$184.22	$184.20	$184.20
Purchase #3	$134.53	12.280%	$151.0503	$151.05	$151.05	$151.10
Purchase #4	$50.80	12.133%	$56.9636	$56.96	$56.95	$57.00
Purchase #5	$194.39	5.756%	$205.5791	$205.58	$205.60	$205.60
Purchase #6	$89.98	11.741%	$100.5446	$100.54	$100.55	$100.50
Purchase #7	$207.65	12.412%	$233.4235	$233.42	$233.40	$233.40
7 purchase totals =	$982.98		$1,085.2381	$1,085.23	$1,085.20	$1,085.30