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	$39.78	10.599%	$43.9963	$44.00	$44.00	$44.00
Purchase #2	$18.32	10.112%	$20.1725	$20.17	$20.15	$20.20
Purchase #3	$146.37	5.117%	$153.8598	$153.86	$153.85	$153.90
Purchase #4	$127.96	9.518%	$140.1392	$140.14	$140.15	$140.10
Purchase #5	$155.65	4.434%	$162.5515	$162.55	$162.55	$162.60
Purchase #6	$86.87	6.719%	$92.7068	$92.71	$92.70	$92.70
Purchase #7	$154.29	13.693%	$175.4169	$175.42	$175.40	$175.40
7 purchase totals =	$729.24		$788.8430	$788.85	$788.80	$788.90