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	$103.73	5.456%	$109.3895	$109.39	$109.40	$109.40
Purchase #2	$196.60	5.839%	$208.0795	$208.08	$208.10	$208.10
Purchase #3	$103.31	13.507%	$117.2641	$117.26	$117.25	$117.30
Purchase #4	$133.52	10.482%	$147.5156	$147.52	$147.50	$147.50
Purchase #5	$116.82	11.301%	$130.0218	$130.02	$130.00	$130.00
Purchase #6	$231.67	4.195%	$241.3886	$241.39	$241.40	$241.40
Purchase #7	$139.83	8.241%	$151.3534	$151.35	$151.35	$151.40
7 purchase totals =	$1,025.48		$1,105.0125	$1,105.01	$1,105.00	$1,105.10