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	$139.70	9.487%	$152.9533	$152.95	$152.95	$153.00
Purchase #2	$112.52	6.151%	$119.4411	$119.44	$119.45	$119.40
Purchase #3	$103.91	7.177%	$111.3676	$111.37	$111.35	$111.40
Purchase #4	$250.45	8.294%	$271.2223	$271.22	$271.20	$271.20
Purchase #5	$148.39	12.784%	$167.3602	$167.36	$167.35	$167.40
Purchase #6	$25.72	13.776%	$29.2632	$29.26	$29.25	$29.30
Purchase #7	$85.58	10.543%	$94.6027	$94.60	$94.60	$94.60
7 purchase totals =	$866.27		$946.2104	$946.20	$946.15	$946.30