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	$14.31	7.845%	$15.4326	$15.43	$15.45	$15.40
Purchase #2	$80.55	5.648%	$85.0995	$85.10	$85.10	$85.10
Purchase #3	$108.47	13.298%	$122.8943	$122.89	$122.90	$122.90
Purchase #4	$77.37	10.168%	$85.237	$85.24	$85.25	$85.20
Purchase #5	$141.52	10.517%	$156.4037	$156.40	$156.40	$156.40
Purchase #6	$86.51	5.259%	$91.0596	$91.06	$91.05	$91.10
Purchase #7	$135.96	7.834%	$146.6111	$146.61	$146.60	$146.60
7 purchase totals =	$644.69		$702.7378	$702.73	$702.75	$702.70