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	$9.53	12.865%	$10.756	$10.76	$10.75	$10.80
Purchase #2	$69.50	12.121%	$77.9241	$77.92	$77.90	$77.90
Purchase #3	$246.29	10.684%	$272.6036	$272.60	$272.60	$272.60
Purchase #4	$62.98	5.737%	$66.5932	$66.59	$66.60	$66.60
Purchase #5	$160.61	11.636%	$179.2986	$179.30	$179.30	$179.30
Purchase #6	$112.50	3.640%	$116.595	$116.60	$116.60	$116.60
Purchase #7	$32.30	13.310%	$36.5991	$36.60	$36.60	$36.60
7 purchase totals =	$693.71		$760.3696	$760.37	$760.35	$760.40