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	$226.85	10.396%	$250.4333	$250.43	$250.45	$250.40
Purchase #2	$231.88	5.573%	$244.8027	$244.80	$244.80	$244.80
Purchase #3	$187.69	3.610%	$194.4656	$194.47	$194.45	$194.50
Purchase #4	$127.87	12.476%	$143.8231	$143.82	$143.80	$143.80
Purchase #5	$164.88	4.408%	$172.1479	$172.15	$172.15	$172.10
Purchase #6	$118.60	13.871%	$135.051	$135.05	$135.05	$135.10
Purchase #7	$79.73	3.798%	$82.7581	$82.76	$82.75	$82.80
7 purchase totals =	$1,137.50		$1,223.4817	$1,223.48	$1,223.45	$1,223.50