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	$175.67	11.837%	$196.4641	$196.46	$196.45	$196.50
Purchase #2	$145.76	8.706%	$158.4499	$158.45	$158.45	$158.40
Purchase #3	$66.71	7.247%	$71.5445	$71.54	$71.55	$71.50
Purchase #4	$46.65	7.247%	$50.0307	$50.03	$50.05	$50.00
Purchase #5	$68.59	8.745%	$74.5882	$74.59	$74.60	$74.60
Purchase #6	$214.40	4.415%	$223.8658	$223.87	$223.85	$223.90
Purchase #7	$59.65	13.285%	$67.5745	$67.57	$67.55	$67.60
7 purchase totals =	$777.43		$842.5177	$842.51	$842.50	$842.50