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	$22.39	13.621%	$25.4397	$25.44	$25.45	$25.40
Purchase #2	$136.40	3.735%	$141.4945	$141.49	$141.50	$141.50
Purchase #3	$159.72	4.786%	$167.3642	$167.36	$167.35	$167.40
Purchase #4	$240.55	4.302%	$250.8985	$250.90	$250.90	$250.90
Purchase #5	$153.92	9.187%	$168.0606	$168.06	$168.05	$168.10
Purchase #6	$98.72	10.338%	$108.9257	$108.93	$108.95	$108.90
Purchase #7	$146.86	7.783%	$158.2901	$158.29	$158.30	$158.30
7 purchase totals =	$958.56		$1,020.4733	$1,020.47	$1,020.50	$1,020.50