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	$243.94	13.712%	$277.3891	$277.39	$277.40	$277.40
Purchase #2	$150.66	10.243%	$166.0921	$166.09	$166.10	$166.10
Purchase #3	$215.74	6.835%	$230.4858	$230.49	$230.50	$230.50
Purchase #4	$198.80	10.635%	$219.9424	$219.94	$219.95	$219.90
Purchase #5	$50.52	5.532%	$53.3148	$53.31	$53.30	$53.30
Purchase #6	$148.49	12.632%	$167.2473	$167.25	$167.25	$167.20
Purchase #7	$50.86	5.386%	$53.5993	$53.60	$53.60	$53.60
7 purchase totals =	$1,059.01		$1,168.0708	$1,168.07	$1,168.10	$1,168.00