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	$52.42	7.503%	$56.3531	$56.35	$56.35	$56.40
Purchase #2	$90.65	10.526%	$100.1918	$100.19	$100.20	$100.20
Purchase #3	$195.48	6.533%	$208.2507	$208.25	$208.25	$208.30
Purchase #4	$222.80	8.409%	$241.5353	$241.54	$241.55	$241.50
Purchase #5	$72.28	10.462%	$79.8419	$79.84	$79.85	$79.80
Purchase #6	$38.81	5.844%	$41.0781	$41.08	$41.10	$41.10
Purchase #7	$74.87	11.592%	$83.5489	$83.55	$83.55	$83.50
7 purchase totals =	$747.31		$810.7998	$810.80	$810.85	$810.80