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	$196.50	12.771%	$221.595	$221.60	$221.60	$221.60
Purchase #2	$34.55	12.704%	$38.9392	$38.94	$38.95	$38.90
Purchase #3	$99.47	4.190%	$103.6378	$103.64	$103.65	$103.60
Purchase #4	$161.46	4.866%	$169.3166	$169.32	$169.30	$169.30
Purchase #5	$193.64	11.128%	$215.1883	$215.19	$215.20	$215.20
Purchase #6	$80.76	12.759%	$91.0642	$91.06	$91.05	$91.10
Purchase #7	$78.64	13.106%	$88.9466	$88.95	$88.95	$88.90
7 purchase totals =	$845.02		$928.6877	$928.70	$928.70	$928.60