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	$173.45	6.268%	$184.3218	$184.32	$184.30	$184.30
Purchase #2	$238.64	6.429%	$253.9822	$253.98	$254.00	$254.00
Purchase #3	$209.44	5.726%	$221.4325	$221.43	$221.45	$221.40
Purchase #4	$90.66	8.136%	$98.0361	$98.04	$98.05	$98.00
Purchase #5	$214.76	12.245%	$241.0574	$241.06	$241.05	$241.10
Purchase #6	$173.56	13.204%	$196.4769	$196.48	$196.50	$196.50
Purchase #7	$61.65	6.140%	$65.4353	$65.44	$65.45	$65.40
7 purchase totals =	$1,162.16		$1,260.7422	$1,260.75	$1,260.80	$1,260.70