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	$39.94	13.549%	$45.3515	$45.35	$45.35	$45.40
Purchase #2	$94.85	5.769%	$100.3219	$100.32	$100.30	$100.30
Purchase #3	$193.35	6.366%	$205.6587	$205.66	$205.65	$205.70
Purchase #4	$155.51	7.660%	$167.4221	$167.42	$167.40	$167.40
Purchase #5	$38.76	6.759%	$41.3798	$41.38	$41.40	$41.40
Purchase #6	$245.49	3.161%	$253.2499	$253.25	$253.25	$253.20
Purchase #7	$118.63	11.464%	$132.2297	$132.23	$132.25	$132.20
7 purchase totals =	$886.53		$945.6136	$945.61	$945.60	$945.60