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	$54.80	13.832%	$62.3799	$62.38	$62.40	$62.40
Purchase #2	$49.28	6.533%	$52.4995	$52.50	$52.50	$52.50
Purchase #3	$67.36	10.661%	$74.5412	$74.54	$74.55	$74.50
Purchase #4	$248.25	7.461%	$266.7719	$266.77	$266.75	$266.80
Purchase #5	$174.61	3.871%	$181.3692	$181.37	$181.35	$181.40
Purchase #6	$30.81	5.240%	$32.4244	$32.42	$32.40	$32.40
Purchase #7	$69.96	3.427%	$72.3575	$72.36	$72.35	$72.40
7 purchase totals =	$695.07		$742.3436	$742.34	$742.30	$742.40