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	$239.74	10.792%	$265.6127	$265.61	$265.60	$265.60
Purchase #2	$139.57	8.371%	$151.2534	$151.25	$151.25	$151.30
Purchase #3	$9.57	7.208%	$10.2598	$10.26	$10.25	$10.30
Purchase #4	$116.43	12.868%	$131.4122	$131.41	$131.40	$131.40
Purchase #5	$235.89	10.144%	$259.8187	$259.82	$259.80	$259.80
Purchase #6	$57.36	9.133%	$62.5987	$62.60	$62.60	$62.60
Purchase #7	$128.92	4.272%	$134.4275	$134.43	$134.45	$134.40
7 purchase totals =	$927.48		$1,015.3830	$1,015.38	$1,015.35	$1,015.40