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	$224.26	11.729%	$250.5635	$250.56	$250.55	$250.60
Purchase #2	$15.73	13.726%	$17.8891	$17.89	$17.90	$17.90
Purchase #3	$45.97	13.710%	$52.2725	$52.27	$52.25	$52.30
Purchase #4	$116.89	9.621%	$128.136	$128.14	$128.15	$128.10
Purchase #5	$141.88	12.509%	$159.6278	$159.63	$159.65	$159.60
Purchase #6	$160.56	11.872%	$179.6217	$179.62	$179.60	$179.60
Purchase #7	$206.94	5.806%	$218.9549	$218.95	$218.95	$219.00
7 purchase totals =	$912.23		$1,007.0655	$1,007.06	$1,007.05	$1,007.10