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	$184.94	11.577%	$206.3505	$206.35	$206.35	$206.40
Purchase #2	$93.54	7.147%	$100.2253	$100.23	$100.25	$100.20
Purchase #3	$34.26	13.433%	$38.8621	$38.86	$38.85	$38.90
Purchase #4	$224.32	7.580%	$241.3235	$241.32	$241.30	$241.30
Purchase #5	$205.51	7.196%	$220.2985	$220.30	$220.30	$220.30
Purchase #6	$235.76	8.262%	$255.2385	$255.24	$255.25	$255.20
Purchase #7	$42.68	6.137%	$45.2993	$45.30	$45.30	$45.30
7 purchase totals =	$1,021.01		$1,107.5977	$1,107.60	$1,107.60	$1,107.60