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	$104.34	9.446%	$114.196	$114.20	$114.20	$114.20
Purchase #2	$68.49	11.818%	$76.5841	$76.58	$76.60	$76.60
Purchase #3	$106.34	7.642%	$114.4665	$114.47	$114.45	$114.50
Purchase #4	$172.78	13.493%	$196.0932	$196.09	$196.10	$196.10
Purchase #5	$170.25	4.787%	$178.3999	$178.40	$178.40	$178.40
Purchase #6	$65.37	11.817%	$73.0948	$73.09	$73.10	$73.10
Purchase #7	$31.47	7.525%	$33.8381	$33.84	$33.85	$33.80
7 purchase totals =	$719.04		$786.6726	$786.67	$786.70	$786.70