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	$236.60	8.120%	$255.8119	$255.81	$255.80	$255.80
Purchase #2	$66.61	11.249%	$74.103	$74.10	$74.10	$74.10
Purchase #3	$95.90	3.637%	$99.3879	$99.39	$99.40	$99.40
Purchase #4	$38.99	5.309%	$41.06	$41.06	$41.05	$41.10
Purchase #5	$80.76	12.668%	$90.9907	$90.99	$91.00	$91.00
Purchase #6	$81.48	11.178%	$90.5878	$90.59	$90.60	$90.60
Purchase #7	$192.81	8.716%	$209.6153	$209.62	$209.60	$209.60
7 purchase totals =	$793.15		$861.5566	$861.56	$861.55	$861.60