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	$48.51	12.643%	$54.6431	$54.64	$54.65	$54.60
Purchase #2	$40.44	6.707%	$43.1523	$43.15	$43.15	$43.20
Purchase #3	$81.79	7.706%	$88.0927	$88.09	$88.10	$88.10
Purchase #4	$47.30	13.298%	$53.59	$53.59	$53.60	$53.60
Purchase #5	$35.88	12.301%	$40.2936	$40.29	$40.30	$40.30
Purchase #6	$47.74	10.431%	$52.7198	$52.72	$52.70	$52.70
Purchase #7	$203.97	5.772%	$215.7431	$215.74	$215.75	$215.70
7 purchase totals =	$505.63		$548.2346	$548.22	$548.25	$548.20