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	$248.68	3.330%	$256.961	$256.96	$256.95	$257.00
Purchase #2	$75.49	10.307%	$83.2708	$83.27	$83.25	$83.30
Purchase #3	$137.50	3.396%	$142.1695	$142.17	$142.15	$142.20
Purchase #4	$175.95	11.524%	$196.2265	$196.23	$196.25	$196.20
Purchase #5	$10.30	3.526%	$10.6632	$10.66	$10.65	$10.70
Purchase #6	$247.76	6.800%	$264.6077	$264.61	$264.60	$264.60
Purchase #7	$46.50	13.692%	$52.8668	$52.87	$52.85	$52.90
7 purchase totals =	$942.18		$1,006.7655	$1,006.77	$1,006.70	$1,006.90