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	$11.82	6.791%	$12.6227	$12.62	$12.60	$12.60
Purchase #2	$242.32	5.426%	$255.4683	$255.47	$255.45	$255.50
Purchase #3	$229.70	6.354%	$244.2951	$244.30	$244.30	$244.30
Purchase #4	$73.76	11.529%	$82.2638	$82.26	$82.25	$82.30
Purchase #5	$144.88	10.793%	$160.5169	$160.52	$160.50	$160.50
Purchase #6	$28.95	11.177%	$32.1857	$32.19	$32.20	$32.20
Purchase #7	$158.43	6.781%	$169.1731	$169.17	$169.15	$169.20
7 purchase totals =	$889.86		$956.5256	$956.53	$956.45	$956.60