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	$118.47	8.511%	$128.553	$128.55	$128.55	$128.60
Purchase #2	$44.48	12.763%	$50.157	$50.16	$50.15	$50.20
Purchase #3	$158.52	7.616%	$170.5929	$170.59	$170.60	$170.60
Purchase #4	$12.82	7.288%	$13.7543	$13.75	$13.75	$13.80
Purchase #5	$214.83	12.597%	$241.8921	$241.89	$241.90	$241.90
Purchase #6	$90.40	11.281%	$100.598	$100.60	$100.60	$100.60
Purchase #7	$202.83	9.853%	$222.8148	$222.81	$222.80	$222.80
7 purchase totals =	$842.35		$928.3621	$928.35	$928.35	$928.50