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	$194.67	3.527%	$201.536	$201.54	$201.55	$201.50
Purchase #2	$91.48	12.704%	$103.1016	$103.10	$103.10	$103.10
Purchase #3	$10.99	5.495%	$11.5939	$11.59	$11.60	$11.60
Purchase #4	$128.98	4.140%	$134.3198	$134.32	$134.30	$134.30
Purchase #5	$95.54	10.552%	$105.6214	$105.62	$105.60	$105.60
Purchase #6	$162.77	4.240%	$169.6714	$169.67	$169.65	$169.70
Purchase #7	$115.61	4.123%	$120.3766	$120.38	$120.40	$120.40
7 purchase totals =	$800.04		$846.2207	$846.22	$846.20	$846.20