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	$174.29	5.328%	$183.5762	$183.58	$183.60	$183.60
Purchase #2	$226.77	13.309%	$256.9508	$256.95	$256.95	$257.00
Purchase #3	$225.38	7.623%	$242.5607	$242.56	$242.55	$242.60
Purchase #4	$61.32	10.174%	$67.5587	$67.56	$67.55	$67.60
Purchase #5	$146.89	7.579%	$158.0228	$158.02	$158.00	$158.00
Purchase #6	$69.53	4.711%	$72.8056	$72.81	$72.80	$72.80
Purchase #7	$214.49	9.348%	$234.5405	$234.54	$234.55	$234.50
7 purchase totals =	$1,118.67		$1,216.0153	$1,216.02	$1,216.00	$1,216.10