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	$154.83	9.659%	$169.785	$169.79	$169.80	$169.80
Purchase #2	$168.71	12.775%	$190.2627	$190.26	$190.25	$190.30
Purchase #3	$111.41	10.558%	$123.1727	$123.17	$123.15	$123.20
Purchase #4	$152.69	5.129%	$160.5215	$160.52	$160.50	$160.50
Purchase #5	$150.65	11.431%	$167.8708	$167.87	$167.85	$167.90
Purchase #6	$198.46	9.334%	$216.9843	$216.98	$217.00	$217.00
Purchase #7	$114.52	5.569%	$120.8976	$120.90	$120.90	$120.90
7 purchase totals =	$1,051.27		$1,149.4946	$1,149.49	$1,149.45	$1,149.60