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	$160.53	13.337%	$181.9399	$181.94	$181.95	$181.90
Purchase #2	$192.83	6.242%	$204.8664	$204.87	$204.85	$204.90
Purchase #3	$113.60	3.237%	$117.2772	$117.28	$117.30	$117.30
Purchase #4	$182.75	8.801%	$198.8338	$198.83	$198.85	$198.80
Purchase #5	$98.85	13.549%	$112.2432	$112.24	$112.25	$112.20
Purchase #6	$64.95	4.505%	$67.876	$67.88	$67.90	$67.90
Purchase #7	$166.50	3.618%	$172.524	$172.52	$172.50	$172.50
7 purchase totals =	$980.01		$1,055.5605	$1,055.56	$1,055.60	$1,055.50