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	$147.91	3.464%	$153.0336	$153.03	$153.05	$153.00
Purchase #2	$91.41	6.668%	$97.5052	$97.51	$97.50	$97.50
Purchase #3	$217.81	6.445%	$231.8479	$231.85	$231.85	$231.80
Purchase #4	$183.25	7.277%	$196.5851	$196.59	$196.60	$196.60
Purchase #5	$82.89	3.721%	$85.9743	$85.97	$85.95	$86.00
Purchase #6	$137.40	6.825%	$146.7776	$146.78	$146.80	$146.80
Purchase #7	$48.52	5.233%	$51.0591	$51.06	$51.05	$51.10
7 purchase totals =	$909.19		$962.7828	$962.79	$962.80	$962.80