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	$216.29	3.530%	$223.925	$223.93	$223.95	$223.90
Purchase #2	$126.62	11.729%	$141.4713	$141.47	$141.45	$141.50
Purchase #3	$45.91	8.873%	$49.9836	$49.98	$50.00	$50.00
Purchase #4	$96.55	3.242%	$99.6802	$99.68	$99.70	$99.70
Purchase #5	$43.29	4.805%	$45.3701	$45.37	$45.35	$45.40
Purchase #6	$173.59	12.491%	$195.2731	$195.27	$195.25	$195.30
Purchase #7	$111.91	7.154%	$119.916	$119.92	$119.90	$119.90
7 purchase totals =	$814.16		$875.6193	$875.62	$875.60	$875.70