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	$102.78	13.298%	$116.4477	$116.45	$116.45	$116.40
Purchase #2	$233.51	3.436%	$241.5334	$241.53	$241.55	$241.50
Purchase #3	$106.40	11.420%	$118.5509	$118.55	$118.55	$118.60
Purchase #4	$71.80	7.847%	$77.4341	$77.43	$77.45	$77.40
Purchase #5	$219.99	6.157%	$233.5348	$233.53	$233.55	$233.50
Purchase #6	$187.95	11.723%	$209.9834	$209.98	$210.00	$210.00
Purchase #7	$154.62	9.213%	$168.8651	$168.87	$168.85	$168.90
7 purchase totals =	$1,077.05		$1,166.3494	$1,166.34	$1,166.40	$1,166.30