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	$169.36	12.366%	$190.3031	$190.30	$190.30	$190.30
Purchase #2	$124.98	9.740%	$137.1531	$137.15	$137.15	$137.20
Purchase #3	$97.86	11.151%	$108.7724	$108.77	$108.75	$108.80
Purchase #4	$206.55	4.127%	$215.0743	$215.07	$215.05	$215.10
Purchase #5	$100.69	8.466%	$109.2144	$109.21	$109.20	$109.20
Purchase #6	$74.67	5.124%	$78.4961	$78.50	$78.50	$78.50
Purchase #7	$217.38	6.688%	$231.9184	$231.92	$231.90	$231.90
7 purchase totals =	$991.49		$1,070.9318	$1,070.92	$1,070.85	$1,071.00