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	$144.59	10.836%	$160.2578	$160.26	$160.25	$160.30
Purchase #2	$243.90	7.400%	$261.9486	$261.95	$261.95	$261.90
Purchase #3	$248.29	9.513%	$271.9098	$271.91	$271.90	$271.90
Purchase #4	$143.95	10.516%	$159.0878	$159.09	$159.10	$159.10
Purchase #5	$143.78	5.191%	$151.2436	$151.24	$151.25	$151.20
Purchase #6	$169.83	5.166%	$178.6034	$178.60	$178.60	$178.60
Purchase #7	$164.80	5.263%	$173.4734	$173.47	$173.45	$173.50
7 purchase totals =	$1,259.14		$1,356.5244	$1,356.52	$1,356.50	$1,356.50