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	$40.83	5.382%	$43.0275	$43.03	$43.05	$43.00
Purchase #2	$59.61	5.787%	$63.0596	$63.06	$63.05	$63.10
Purchase #3	$18.94	9.704%	$20.7779	$20.78	$20.80	$20.80
Purchase #4	$78.78	13.379%	$89.32	$89.32	$89.30	$89.30
Purchase #5	$36.68	6.714%	$39.1427	$39.14	$39.15	$39.10
Purchase #6	$43.74	11.449%	$48.7478	$48.75	$48.75	$48.70
Purchase #7	$240.81	9.239%	$263.0584	$263.06	$263.05	$263.10
7 purchase totals =	$519.39		$567.1339	$567.14	$567.15	$567.10