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	$32.71	3.181%	$33.7505	$33.75	$33.75	$33.80
Purchase #2	$91.53	4.742%	$95.8704	$95.87	$95.85	$95.90
Purchase #3	$133.85	7.851%	$144.3586	$144.36	$144.35	$144.40
Purchase #4	$168.31	9.583%	$184.4391	$184.44	$184.45	$184.40
Purchase #5	$166.90	3.545%	$172.8166	$172.82	$172.80	$172.80
Purchase #6	$231.31	13.104%	$261.6209	$261.62	$261.60	$261.60
Purchase #7	$121.30	6.471%	$129.1493	$129.15	$129.15	$129.10
7 purchase totals =	$945.91		$1,022.0054	$1,022.01	$1,021.95	$1,022.00