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	$50.85	3.301%	$52.5286	$52.53	$52.55	$52.50
Purchase #2	$13.97	4.167%	$14.5521	$14.55	$14.55	$14.60
Purchase #3	$158.43	5.758%	$167.5524	$167.55	$167.55	$167.60
Purchase #4	$19.40	9.480%	$21.2391	$21.24	$21.25	$21.20
Purchase #5	$205.71	11.673%	$229.7225	$229.72	$229.70	$229.70
Purchase #6	$13.50	5.636%	$14.2609	$14.26	$14.25	$14.30
Purchase #7	$40.42	12.741%	$45.5699	$45.57	$45.55	$45.60
7 purchase totals =	$502.28		$545.4255	$545.42	$545.40	$545.50