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	$170.81	9.839%	$187.616	$187.62	$187.60	$187.60
Purchase #2	$231.67	10.755%	$256.5861	$256.59	$256.60	$256.60
Purchase #3	$145.95	10.564%	$161.3682	$161.37	$161.35	$161.40
Purchase #4	$206.31	12.705%	$232.5217	$232.52	$232.50	$232.50
Purchase #5	$67.53	3.242%	$69.7193	$69.72	$69.70	$69.70
Purchase #6	$16.61	5.435%	$17.5128	$17.51	$17.50	$17.50
Purchase #7	$91.27	9.384%	$99.8348	$99.83	$99.85	$99.80
7 purchase totals =	$930.15		$1,025.1589	$1,025.16	$1,025.10	$1,025.10