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	$151.32	8.811%	$164.6528	$164.65	$164.65	$164.70
Purchase #2	$80.89	4.862%	$84.8229	$84.82	$84.80	$84.80
Purchase #3	$40.58	10.698%	$44.9212	$44.92	$44.90	$44.90
Purchase #4	$200.89	7.213%	$215.3802	$215.38	$215.40	$215.40
Purchase #5	$138.46	13.309%	$156.8876	$156.89	$156.90	$156.90
Purchase #6	$11.77	6.194%	$12.499	$12.50	$12.50	$12.50
Purchase #7	$95.35	8.651%	$103.5987	$103.60	$103.60	$103.60
7 purchase totals =	$719.26		$782.7624	$782.76	$782.75	$782.80