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	$56.40	8.375%	$61.1235	$61.12	$61.10	$61.10
Purchase #2	$132.49	6.146%	$140.6328	$140.63	$140.65	$140.60
Purchase #3	$245.28	4.206%	$255.5965	$255.60	$255.60	$255.60
Purchase #4	$164.91	10.615%	$182.4152	$182.42	$182.40	$182.40
Purchase #5	$141.50	7.309%	$151.8422	$151.84	$151.85	$151.80
Purchase #6	$48.93	10.818%	$54.2232	$54.22	$54.20	$54.20
Purchase #7	$133.84	4.451%	$139.7972	$139.80	$139.80	$139.80
7 purchase totals =	$923.35		$985.6306	$985.63	$985.60	$985.50