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	$33.72	11.378%	$37.5567	$37.56	$37.55	$37.60
Purchase #2	$213.47	9.420%	$233.5789	$233.58	$233.60	$233.60
Purchase #3	$250.64	4.444%	$261.7784	$261.78	$261.80	$261.80
Purchase #4	$59.65	5.517%	$62.9409	$62.94	$62.95	$62.90
Purchase #5	$114.95	10.638%	$127.1784	$127.18	$127.20	$127.20
Purchase #6	$66.39	8.852%	$72.2668	$72.27	$72.25	$72.30
Purchase #7	$234.94	11.121%	$261.0677	$261.07	$261.05	$261.10
7 purchase totals =	$973.76		$1,056.3678	$1,056.38	$1,056.40	$1,056.50