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	$152.72	7.401%	$164.0228	$164.02	$164.00	$164.00
Purchase #2	$238.70	7.504%	$256.612	$256.61	$256.60	$256.60
Purchase #3	$205.68	7.476%	$221.0566	$221.06	$221.05	$221.10
Purchase #4	$101.87	10.486%	$112.5521	$112.55	$112.55	$112.60
Purchase #5	$71.93	4.639%	$75.2668	$75.27	$75.25	$75.30
Purchase #6	$49.58	10.555%	$54.8132	$54.81	$54.80	$54.80
Purchase #7	$178.39	3.431%	$184.5106	$184.51	$184.50	$184.50
7 purchase totals =	$998.87		$1,068.8341	$1,068.83	$1,068.75	$1,068.90