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	$105.36	5.622%	$111.2833	$111.28	$111.30	$111.30
Purchase #2	$179.31	3.777%	$186.0825	$186.08	$186.10	$186.10
Purchase #3	$220.84	9.117%	$240.974	$240.97	$240.95	$241.00
Purchase #4	$156.28	5.733%	$165.2395	$165.24	$165.25	$165.20
Purchase #5	$68.71	10.391%	$75.8497	$75.85	$75.85	$75.80
Purchase #6	$69.83	12.593%	$78.6237	$78.62	$78.60	$78.60
Purchase #7	$150.60	9.654%	$165.1389	$165.14	$165.15	$165.10
7 purchase totals =	$950.93		$1,023.1916	$1,023.18	$1,023.20	$1,023.10