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	$153.60	9.190%	$167.7158	$167.72	$167.70	$167.70
Purchase #2	$109.28	9.628%	$119.8015	$119.80	$119.80	$119.80
Purchase #3	$133.84	13.775%	$152.2765	$152.28	$152.30	$152.30
Purchase #4	$153.33	5.584%	$161.8919	$161.89	$161.90	$161.90
Purchase #5	$59.44	11.292%	$66.152	$66.15	$66.15	$66.20
Purchase #6	$58.53	6.703%	$62.4533	$62.45	$62.45	$62.50
Purchase #7	$54.33	3.754%	$56.3695	$56.37	$56.35	$56.40
7 purchase totals =	$722.35		$786.6605	$786.66	$786.65	$786.80