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	$79.74	13.606%	$90.5894	$90.59	$90.60	$90.60
Purchase #2	$41.99	3.366%	$43.4034	$43.40	$43.40	$43.40
Purchase #3	$173.83	10.318%	$191.7658	$191.77	$191.75	$191.80
Purchase #4	$189.27	3.488%	$195.8717	$195.87	$195.85	$195.90
Purchase #5	$97.63	7.561%	$105.0118	$105.01	$105.00	$105.00
Purchase #6	$195.98	5.403%	$206.5688	$206.57	$206.55	$206.60
Purchase #7	$190.98	12.145%	$214.1745	$214.17	$214.15	$214.20
7 purchase totals =	$969.42		$1,047.3854	$1,047.38	$1,047.30	$1,047.50