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	$121.86	8.469%	$132.1803	$132.18	$132.20	$132.20
Purchase #2	$90.25	11.277%	$100.4275	$100.43	$100.45	$100.40
Purchase #3	$35.40	3.243%	$36.548	$36.55	$36.55	$36.50
Purchase #4	$53.30	4.805%	$55.8611	$55.86	$55.85	$55.90
Purchase #5	$154.34	9.671%	$169.2662	$169.27	$169.25	$169.30
Purchase #6	$169.74	6.600%	$180.9428	$180.94	$180.95	$180.90
Purchase #7	$88.39	13.832%	$100.6161	$100.62	$100.60	$100.60
7 purchase totals =	$713.28		$775.8420	$775.85	$775.85	$775.80