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	$205.37	5.732%	$217.1418	$217.14	$217.15	$217.10
Purchase #2	$215.28	3.410%	$222.621	$222.62	$222.60	$222.60
Purchase #3	$90.54	3.294%	$93.5224	$93.52	$93.50	$93.50
Purchase #4	$37.30	13.872%	$42.4743	$42.47	$42.45	$42.50
Purchase #5	$41.66	4.479%	$43.526	$43.53	$43.55	$43.50
Purchase #6	$179.25	6.211%	$190.3832	$190.38	$190.40	$190.40
Purchase #7	$157.75	8.144%	$170.5972	$170.60	$170.60	$170.60
7 purchase totals =	$927.15		$980.2659	$980.26	$980.25	$980.20