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	$38.41	10.139%	$42.3044	$42.30	$42.30	$42.30
Purchase #2	$177.52	6.278%	$188.6647	$188.66	$188.65	$188.70
Purchase #3	$199.48	11.501%	$222.4222	$222.42	$222.40	$222.40
Purchase #4	$59.51	9.177%	$64.9712	$64.97	$64.95	$65.00
Purchase #5	$143.93	11.369%	$160.2934	$160.29	$160.30	$160.30
Purchase #6	$214.69	10.835%	$237.9517	$237.95	$237.95	$238.00
Purchase #7	$167.60	11.472%	$186.8271	$186.83	$186.85	$186.80
7 purchase totals =	$1,001.14		$1,103.4347	$1,103.42	$1,103.40	$1,103.50