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	$63.30	6.738%	$67.5652	$67.57	$67.55	$67.60
Purchase #2	$117.90	5.688%	$124.6062	$124.61	$124.60	$124.60
Purchase #3	$26.30	3.739%	$27.2834	$27.28	$27.30	$27.30
Purchase #4	$59.62	3.232%	$61.5469	$61.55	$61.55	$61.50
Purchase #5	$215.90	6.514%	$229.9637	$229.96	$229.95	$230.00
Purchase #6	$138.77	10.479%	$153.3117	$153.31	$153.30	$153.30
Purchase #7	$10.85	4.482%	$11.3363	$11.34	$11.35	$11.30
7 purchase totals =	$632.64		$675.6134	$675.62	$675.60	$675.60