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	$120.83	5.533%	$127.5155	$127.52	$127.50	$127.50
Purchase #2	$139.90	12.673%	$157.6295	$157.63	$157.65	$157.60
Purchase #3	$223.93	4.338%	$233.6441	$233.64	$233.65	$233.60
Purchase #4	$65.27	10.599%	$72.188	$72.19	$72.20	$72.20
Purchase #5	$211.78	5.644%	$223.7329	$223.73	$223.75	$223.70
Purchase #6	$241.60	3.687%	$250.5078	$250.51	$250.50	$250.50
Purchase #7	$35.28	10.711%	$39.0588	$39.06	$39.05	$39.10
7 purchase totals =	$1,038.59		$1,104.2766	$1,104.28	$1,104.30	$1,104.20