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	$221.34	5.539%	$233.6	$233.60	$233.60	$233.60
Purchase #2	$204.69	13.278%	$231.8687	$231.87	$231.85	$231.90
Purchase #3	$174.28	6.573%	$185.7354	$185.74	$185.75	$185.70
Purchase #4	$5.52	3.348%	$5.7048	$5.70	$5.70	$5.70
Purchase #5	$10.60	11.820%	$11.8529	$11.85	$11.85	$11.90
Purchase #6	$39.99	6.446%	$42.5678	$42.57	$42.55	$42.60
Purchase #7	$177.35	5.173%	$186.5243	$186.52	$186.50	$186.50
7 purchase totals =	$833.77		$897.8539	$897.85	$897.80	$897.90