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	$13.64	3.707%	$14.1456	$14.15	$14.15	$14.10
Purchase #2	$241.91	13.203%	$273.8494	$273.85	$273.85	$273.80
Purchase #3	$207.28	9.773%	$227.5375	$227.54	$227.55	$227.50
Purchase #4	$39.86	9.135%	$43.5012	$43.50	$43.50	$43.50
Purchase #5	$30.52	7.304%	$32.7492	$32.75	$32.75	$32.70
Purchase #6	$105.56	10.289%	$116.4211	$116.42	$116.40	$116.40
Purchase #7	$16.97	6.417%	$18.059	$18.06	$18.05	$18.10
7 purchase totals =	$655.74		$726.2630	$726.27	$726.25	$726.10