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	$212.83	10.691%	$235.5837	$235.58	$235.60	$235.60
Purchase #2	$173.56	3.210%	$179.1313	$179.13	$179.15	$179.10
Purchase #3	$85.28	10.776%	$94.4698	$94.47	$94.45	$94.50
Purchase #4	$119.28	6.529%	$127.0678	$127.07	$127.05	$127.10
Purchase #5	$139.33	3.587%	$144.3278	$144.33	$144.35	$144.30
Purchase #6	$11.36	6.388%	$12.0857	$12.09	$12.10	$12.10
Purchase #7	$136.75	6.234%	$145.275	$145.28	$145.30	$145.30
7 purchase totals =	$878.39		$937.9411	$937.95	$938.00	$938.00