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	$172.77	11.293%	$192.2809	$192.28	$192.30	$192.30
Purchase #2	$192.43	6.581%	$205.0938	$205.09	$205.10	$205.10
Purchase #3	$155.54	7.703%	$167.5212	$167.52	$167.50	$167.50
Purchase #4	$200.32	12.514%	$225.388	$225.39	$225.40	$225.40
Purchase #5	$97.74	6.570%	$104.1615	$104.16	$104.15	$104.20
Purchase #6	$36.81	4.246%	$38.373	$38.37	$38.35	$38.40
Purchase #7	$149.56	6.859%	$159.8183	$159.82	$159.80	$159.80
7 purchase totals =	$1,005.17		$1,092.6367	$1,092.63	$1,092.60	$1,092.70