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	$242.86	6.446%	$258.5148	$258.51	$258.50	$258.50
Purchase #2	$86.61	10.383%	$95.6027	$95.60	$95.60	$95.60
Purchase #3	$126.89	4.170%	$132.1813	$132.18	$132.20	$132.20
Purchase #4	$191.91	13.567%	$217.9464	$217.95	$217.95	$217.90
Purchase #5	$28.28	4.344%	$29.5085	$29.51	$29.50	$29.50
Purchase #6	$176.92	11.406%	$197.0995	$197.10	$197.10	$197.10
Purchase #7	$76.60	11.482%	$85.3952	$85.40	$85.40	$85.40
7 purchase totals =	$930.07		$1,016.2484	$1,016.25	$1,016.25	$1,016.20