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	$132.37	9.462%	$144.8948	$144.89	$144.90	$144.90
Purchase #2	$205.44	4.260%	$214.1917	$214.19	$214.20	$214.20
Purchase #3	$78.68	13.645%	$89.4159	$89.42	$89.40	$89.40
Purchase #4	$144.65	13.118%	$163.6252	$163.63	$163.65	$163.60
Purchase #5	$32.54	3.235%	$33.5927	$33.59	$33.60	$33.60
Purchase #6	$207.63	6.697%	$221.535	$221.54	$221.55	$221.50
Purchase #7	$159.54	8.419%	$172.9717	$172.97	$172.95	$173.00
7 purchase totals =	$960.85		$1,040.2270	$1,040.23	$1,040.25	$1,040.20