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	$70.87	10.553%	$78.3489	$78.35	$78.35	$78.30
Purchase #2	$241.51	6.228%	$256.5512	$256.55	$256.55	$256.60
Purchase #3	$115.61	4.289%	$120.5685	$120.57	$120.55	$120.60
Purchase #4	$26.32	3.548%	$27.2538	$27.25	$27.25	$27.30
Purchase #5	$247.60	3.202%	$255.5282	$255.53	$255.55	$255.50
Purchase #6	$222.77	3.752%	$231.1283	$231.13	$231.15	$231.10
Purchase #7	$132.66	7.387%	$142.4596	$142.46	$142.45	$142.50
7 purchase totals =	$1,057.34		$1,111.8385	$1,111.84	$1,111.85	$1,111.90