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	$37.92	13.784%	$43.1469	$43.15	$43.15	$43.10
Purchase #2	$21.96	11.108%	$24.3993	$24.40	$24.40	$24.40
Purchase #3	$127.82	10.231%	$140.8973	$140.90	$140.90	$140.90
Purchase #4	$146.56	3.559%	$151.7761	$151.78	$151.80	$151.80
Purchase #5	$112.77	10.328%	$124.4169	$124.42	$124.40	$124.40
Purchase #6	$135.27	5.340%	$142.4934	$142.49	$142.50	$142.50
Purchase #7	$74.42	6.479%	$79.2417	$79.24	$79.25	$79.20
7 purchase totals =	$656.72		$706.3716	$706.38	$706.40	$706.30