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	$20.69	9.443%	$22.6438	$22.64	$22.65	$22.60
Purchase #2	$68.77	10.312%	$75.8616	$75.86	$75.85	$75.90
Purchase #3	$158.72	10.528%	$175.43	$175.43	$175.45	$175.40
Purchase #4	$241.76	12.345%	$271.6053	$271.61	$271.60	$271.60
Purchase #5	$138.91	3.496%	$143.7663	$143.77	$143.75	$143.80
Purchase #6	$161.52	4.409%	$168.6414	$168.64	$168.65	$168.60
Purchase #7	$209.60	13.711%	$238.3383	$238.34	$238.35	$238.30
7 purchase totals =	$999.97		$1,096.2867	$1,096.29	$1,096.30	$1,096.20