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	$80.76	12.520%	$90.8712	$90.87	$90.85	$90.90
Purchase #2	$153.31	3.110%	$158.0779	$158.08	$158.10	$158.10
Purchase #3	$191.49	7.451%	$205.7579	$205.76	$205.75	$205.80
Purchase #4	$249.76	3.276%	$257.9421	$257.94	$257.95	$257.90
Purchase #5	$169.35	11.525%	$188.8676	$188.87	$188.85	$188.90
Purchase #6	$242.89	4.426%	$253.6403	$253.64	$253.65	$253.60
Purchase #7	$208.47	8.360%	$225.8981	$225.90	$225.90	$225.90
7 purchase totals =	$1,296.03		$1,381.0551	$1,381.06	$1,381.05	$1,381.10