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	$35.55	9.309%	$38.8593	$38.86	$38.85	$38.90
Purchase #2	$94.40	4.248%	$98.4101	$98.41	$98.40	$98.40
Purchase #3	$213.89	10.140%	$235.5784	$235.58	$235.60	$235.60
Purchase #4	$202.28	3.821%	$210.0091	$210.01	$210.00	$210.00
Purchase #5	$56.92	13.307%	$64.4943	$64.49	$64.50	$64.50
Purchase #6	$128.50	10.516%	$142.0131	$142.01	$142.00	$142.00
Purchase #7	$127.63	13.121%	$144.3763	$144.38	$144.40	$144.40
7 purchase totals =	$859.17		$933.7406	$933.74	$933.75	$933.80