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	$132.39	11.103%	$147.0893	$147.09	$147.10	$147.10
Purchase #2	$178.51	8.525%	$193.728	$193.73	$193.75	$193.70
Purchase #3	$90.75	10.290%	$100.0882	$100.09	$100.10	$100.10
Purchase #4	$83.72	8.130%	$90.5264	$90.53	$90.55	$90.50
Purchase #5	$19.57	13.664%	$22.244	$22.24	$22.25	$22.20
Purchase #6	$40.50	7.279%	$43.448	$43.45	$43.45	$43.40
Purchase #7	$9.42	5.525%	$9.9405	$9.94	$9.95	$9.90
7 purchase totals =	$554.86		$607.0644	$607.07	$607.15	$606.90