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	$146.44	5.747%	$154.8559	$154.86	$154.85	$154.90
Purchase #2	$247.44	6.635%	$263.8576	$263.86	$263.85	$263.90
Purchase #3	$106.56	10.351%	$117.59	$117.59	$117.60	$117.60
Purchase #4	$10.43	3.718%	$10.8178	$10.82	$10.80	$10.80
Purchase #5	$137.55	11.571%	$153.4659	$153.47	$153.45	$153.50
Purchase #6	$47.52	12.314%	$53.3716	$53.37	$53.35	$53.40
Purchase #7	$103.55	13.390%	$117.4153	$117.42	$117.40	$117.40
7 purchase totals =	$799.49		$871.3741	$871.39	$871.30	$871.50