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	$108.29	7.581%	$116.4995	$116.50	$116.50	$116.50
Purchase #2	$162.51	10.525%	$179.6142	$179.61	$179.60	$179.60
Purchase #3	$169.45	9.379%	$185.3427	$185.34	$185.35	$185.30
Purchase #4	$27.95	7.245%	$29.975	$29.98	$30.00	$30.00
Purchase #5	$140.33	11.776%	$156.8553	$156.86	$156.85	$156.90
Purchase #6	$237.40	10.496%	$262.3175	$262.32	$262.30	$262.30
Purchase #7	$161.98	7.232%	$173.6944	$173.69	$173.70	$173.70
7 purchase totals =	$1,007.91		$1,104.2986	$1,104.30	$1,104.30	$1,104.30