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	$156.61	7.648%	$168.5875	$168.59	$168.60	$168.60
Purchase #2	$52.62	10.458%	$58.123	$58.12	$58.10	$58.10
Purchase #3	$223.32	4.817%	$234.0773	$234.08	$234.10	$234.10
Purchase #4	$70.32	10.112%	$77.4308	$77.43	$77.45	$77.40
Purchase #5	$118.35	7.691%	$127.4523	$127.45	$127.45	$127.50
Purchase #6	$74.89	5.667%	$79.134	$79.13	$79.15	$79.10
Purchase #7	$14.51	9.626%	$15.9067	$15.91	$15.90	$15.90
7 purchase totals =	$710.62		$760.7116	$760.71	$760.75	$760.70