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	$95.94	9.679%	$105.226	$105.23	$105.25	$105.20
Purchase #2	$211.26	6.749%	$225.5179	$225.52	$225.50	$225.50
Purchase #3	$120.25	10.460%	$132.8282	$132.83	$132.85	$132.80
Purchase #4	$119.31	6.841%	$127.472	$127.47	$127.45	$127.50
Purchase #5	$169.78	10.441%	$187.5067	$187.51	$187.50	$187.50
Purchase #6	$158.83	9.112%	$173.3026	$173.30	$173.30	$173.30
Purchase #7	$84.95	7.205%	$91.0706	$91.07	$91.05	$91.10
7 purchase totals =	$960.32		$1,042.9240	$1,042.93	$1,042.90	$1,042.90