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	$20.75	4.727%	$21.7309	$21.73	$21.75	$21.70
Purchase #2	$105.46	12.374%	$118.5096	$118.51	$118.50	$118.50
Purchase #3	$147.97	6.160%	$157.085	$157.09	$157.10	$157.10
Purchase #4	$233.27	13.528%	$264.8268	$264.83	$264.85	$264.80
Purchase #5	$163.87	13.451%	$185.9122	$185.91	$185.90	$185.90
Purchase #6	$189.42	5.540%	$199.9139	$199.91	$199.90	$199.90
Purchase #7	$96.72	7.515%	$103.9885	$103.99	$104.00	$104.00
7 purchase totals =	$957.46		$1,051.9669	$1,051.97	$1,052.00	$1,051.90