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	$7.28	6.779%	$7.7735	$7.77	$7.75	$7.80
Purchase #2	$11.61	8.377%	$12.5826	$12.58	$12.60	$12.60
Purchase #3	$21.52	11.546%	$24.0047	$24.00	$24.00	$24.00
Purchase #4	$61.56	6.366%	$65.4789	$65.48	$65.50	$65.50
Purchase #5	$173.43	8.246%	$187.731	$187.73	$187.75	$187.70
Purchase #6	$198.64	10.385%	$219.2688	$219.27	$219.25	$219.30
Purchase #7	$40.45	7.433%	$43.4566	$43.46	$43.45	$43.50
7 purchase totals =	$514.49		$560.2961	$560.29	$560.30	$560.40