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	$238.81	6.867%	$255.2091	$255.21	$255.20	$255.20
Purchase #2	$99.43	3.416%	$102.8265	$102.83	$102.85	$102.80
Purchase #3	$147.29	7.560%	$158.4251	$158.43	$158.45	$158.40
Purchase #4	$201.31	6.678%	$214.7535	$214.75	$214.75	$214.80
Purchase #5	$10.37	10.249%	$11.4328	$11.43	$11.45	$11.40
Purchase #6	$227.41	3.215%	$234.7212	$234.72	$234.70	$234.70
Purchase #7	$33.40	5.464%	$35.225	$35.23	$35.25	$35.20
7 purchase totals =	$958.02		$1,012.5932	$1,012.60	$1,012.65	$1,012.50