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	$189.93	11.588%	$211.9391	$211.94	$211.95	$211.90
Purchase #2	$233.79	10.188%	$257.6085	$257.61	$257.60	$257.60
Purchase #3	$216.71	6.579%	$230.9674	$230.97	$230.95	$231.00
Purchase #4	$25.29	13.295%	$28.6523	$28.65	$28.65	$28.70
Purchase #5	$67.38	6.824%	$71.978	$71.98	$72.00	$72.00
Purchase #6	$133.45	3.119%	$137.6123	$137.61	$137.60	$137.60
Purchase #7	$70.93	9.286%	$77.5166	$77.52	$77.50	$77.50
7 purchase totals =	$937.48		$1,016.2742	$1,016.28	$1,016.25	$1,016.30