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	$59.36	8.774%	$64.5682	$64.57	$64.55	$64.60
Purchase #2	$45.50	8.676%	$49.4476	$49.45	$49.45	$49.40
Purchase #3	$140.45	10.499%	$155.1958	$155.20	$155.20	$155.20
Purchase #4	$137.39	11.810%	$153.6158	$153.62	$153.60	$153.60
Purchase #5	$178.71	7.169%	$191.5217	$191.52	$191.50	$191.50
Purchase #6	$85.61	5.522%	$90.3374	$90.34	$90.35	$90.30
Purchase #7	$196.59	12.111%	$220.399	$220.40	$220.40	$220.40
7 purchase totals =	$843.61		$925.0855	$925.10	$925.05	$925.00