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	$56.83	10.366%	$62.721	$62.72	$62.70	$62.70
Purchase #2	$27.40	11.749%	$30.6192	$30.62	$30.60	$30.60
Purchase #3	$216.84	9.818%	$238.1294	$238.13	$238.15	$238.10
Purchase #4	$132.86	10.300%	$146.5446	$146.54	$146.55	$146.50
Purchase #5	$216.32	4.703%	$226.4935	$226.49	$226.50	$226.50
Purchase #6	$89.76	11.714%	$100.2745	$100.27	$100.25	$100.30
Purchase #7	$211.97	5.706%	$224.065	$224.07	$224.05	$224.10
7 purchase totals =	$951.98		$1,028.8472	$1,028.84	$1,028.80	$1,028.80