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	$214.96	10.795%	$238.1649	$238.16	$238.15	$238.20
Purchase #2	$173.89	13.248%	$196.9269	$196.93	$196.95	$196.90
Purchase #3	$173.67	10.226%	$191.4295	$191.43	$191.45	$191.40
Purchase #4	$160.34	13.574%	$182.1046	$182.10	$182.10	$182.10
Purchase #5	$35.64	9.370%	$38.9795	$38.98	$39.00	$39.00
Purchase #6	$60.98	5.614%	$64.4034	$64.40	$64.40	$64.40
Purchase #7	$112.65	13.327%	$127.6629	$127.66	$127.65	$127.70
7 purchase totals =	$932.13		$1,039.6717	$1,039.66	$1,039.70	$1,039.70