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	$55.58	12.694%	$62.6353	$62.64	$62.65	$62.60
Purchase #2	$84.84	10.233%	$93.5217	$93.52	$93.50	$93.50
Purchase #3	$224.78	13.155%	$254.3498	$254.35	$254.35	$254.30
Purchase #4	$9.95	5.369%	$10.4842	$10.48	$10.50	$10.50
Purchase #5	$30.92	3.237%	$31.9209	$31.92	$31.90	$31.90
Purchase #6	$96.51	4.183%	$100.547	$100.55	$100.55	$100.50
Purchase #7	$224.98	7.732%	$242.3755	$242.38	$242.40	$242.40
7 purchase totals =	$727.56		$795.8344	$795.84	$795.85	$795.70