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	$132.72	7.181%	$142.2506	$142.25	$142.25	$142.30
Purchase #2	$146.47	12.730%	$165.1156	$165.12	$165.10	$165.10
Purchase #3	$39.52	12.739%	$44.5545	$44.55	$44.55	$44.60
Purchase #4	$93.69	11.375%	$104.3472	$104.35	$104.35	$104.30
Purchase #5	$109.72	7.699%	$118.1673	$118.17	$118.15	$118.20
Purchase #6	$67.69	10.560%	$74.8381	$74.84	$74.85	$74.80
Purchase #7	$127.27	10.285%	$140.3597	$140.36	$140.35	$140.40
7 purchase totals =	$717.08		$789.6330	$789.64	$789.60	$789.70