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	$87.73	5.558%	$92.606	$92.61	$92.60	$92.60
Purchase #2	$75.37	8.162%	$81.5217	$81.52	$81.50	$81.50
Purchase #3	$150.32	13.650%	$170.8387	$170.84	$170.85	$170.80
Purchase #4	$142.38	6.227%	$151.246	$151.25	$151.25	$151.20
Purchase #5	$73.43	11.561%	$81.9192	$81.92	$81.90	$81.90
Purchase #6	$139.89	3.771%	$145.1653	$145.17	$145.15	$145.20
Purchase #7	$194.56	11.700%	$217.3235	$217.32	$217.30	$217.30
7 purchase totals =	$863.68		$940.6204	$940.63	$940.55	$940.50