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	$67.58	7.406%	$72.585	$72.59	$72.60	$72.60
Purchase #2	$220.62	4.788%	$231.1833	$231.18	$231.20	$231.20
Purchase #3	$215.64	11.321%	$240.0526	$240.05	$240.05	$240.10
Purchase #4	$37.54	10.204%	$41.3706	$41.37	$41.35	$41.40
Purchase #5	$185.89	12.295%	$208.7452	$208.75	$208.75	$208.70
Purchase #6	$94.34	11.298%	$104.9985	$105.00	$105.00	$105.00
Purchase #7	$209.25	13.646%	$237.8043	$237.80	$237.80	$237.80
7 purchase totals =	$1,030.86		$1,136.7395	$1,136.74	$1,136.75	$1,136.80