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	$234.87	10.677%	$259.9471	$259.95	$259.95	$259.90
Purchase #2	$228.82	4.258%	$238.5632	$238.56	$238.55	$238.60
Purchase #3	$83.81	12.816%	$94.5511	$94.55	$94.55	$94.60
Purchase #4	$239.83	7.247%	$257.2105	$257.21	$257.20	$257.20
Purchase #5	$97.52	8.367%	$105.6795	$105.68	$105.70	$105.70
Purchase #6	$48.43	6.363%	$51.5116	$51.51	$51.50	$51.50
Purchase #7	$40.38	4.731%	$42.2904	$42.29	$42.30	$42.30
7 purchase totals =	$973.66		$1,049.7534	$1,049.75	$1,049.75	$1,049.80