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	$202.78	6.389%	$215.7356	$215.74	$215.75	$215.70
Purchase #2	$121.94	4.542%	$127.4785	$127.48	$127.50	$127.50
Purchase #3	$75.66	8.532%	$82.1153	$82.12	$82.10	$82.10
Purchase #4	$47.38	6.246%	$50.3394	$50.34	$50.35	$50.30
Purchase #5	$241.31	5.660%	$254.9681	$254.97	$254.95	$255.00
Purchase #6	$230.59	8.459%	$250.0956	$250.10	$250.10	$250.10
Purchase #7	$247.84	6.861%	$264.8443	$264.84	$264.85	$264.80
7 purchase totals =	$1,167.50		$1,245.5768	$1,245.59	$1,245.60	$1,245.50