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	$99.95	10.498%	$110.4428	$110.44	$110.45	$110.40
Purchase #2	$142.72	7.690%	$153.6952	$153.70	$153.70	$153.70
Purchase #3	$76.96	6.119%	$81.6692	$81.67	$81.65	$81.70
Purchase #4	$157.43	5.340%	$165.8368	$165.84	$165.85	$165.80
Purchase #5	$51.60	4.773%	$54.0629	$54.06	$54.05	$54.10
Purchase #6	$249.94	9.186%	$272.8995	$272.90	$272.90	$272.90
Purchase #7	$166.86	7.144%	$178.7805	$178.78	$178.80	$178.80
7 purchase totals =	$945.46		$1,017.3869	$1,017.39	$1,017.40	$1,017.40