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	$139.26	10.274%	$153.5676	$153.57	$153.55	$153.60
Purchase #2	$5.80	13.763%	$6.5983	$6.60	$6.60	$6.60
Purchase #3	$207.85	7.470%	$223.3764	$223.38	$223.40	$223.40
Purchase #4	$145.82	13.739%	$165.8542	$165.85	$165.85	$165.90
Purchase #5	$84.82	6.762%	$90.5555	$90.56	$90.55	$90.60
Purchase #6	$214.55	4.624%	$224.4708	$224.47	$224.45	$224.50
Purchase #7	$178.56	5.502%	$188.3844	$188.38	$188.40	$188.40
7 purchase totals =	$976.66		$1,052.8072	$1,052.81	$1,052.80	$1,053.00