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	$144.25	4.749%	$151.1004	$151.10	$151.10	$151.10
Purchase #2	$156.54	7.564%	$168.3807	$168.38	$168.40	$168.40
Purchase #3	$197.38	10.243%	$217.5976	$217.60	$217.60	$217.60
Purchase #4	$230.74	7.140%	$247.2148	$247.21	$247.20	$247.20
Purchase #5	$29.45	10.872%	$32.6518	$32.65	$32.65	$32.70
Purchase #6	$16.43	6.493%	$17.4968	$17.50	$17.50	$17.50
Purchase #7	$73.31	7.115%	$78.526	$78.53	$78.55	$78.50
7 purchase totals =	$848.10		$912.9681	$912.97	$913.00	$913.00