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	$168.98	9.694%	$185.3609	$185.36	$185.35	$185.40
Purchase #2	$171.49	11.131%	$190.5786	$190.58	$190.60	$190.60
Purchase #3	$176.31	13.396%	$199.9285	$199.93	$199.95	$199.90
Purchase #4	$230.58	7.204%	$247.191	$247.19	$247.20	$247.20
Purchase #5	$38.36	10.333%	$42.3237	$42.32	$42.30	$42.30
Purchase #6	$94.69	9.430%	$103.6193	$103.62	$103.60	$103.60
Purchase #7	$232.54	6.577%	$247.8342	$247.83	$247.85	$247.80
7 purchase totals =	$1,112.95		$1,216.8362	$1,216.83	$1,216.85	$1,216.80