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	$149.59	4.758%	$156.7075	$156.71	$156.70	$156.70
Purchase #2	$101.77	12.462%	$114.4526	$114.45	$114.45	$114.50
Purchase #3	$156.89	11.458%	$174.8665	$174.87	$174.85	$174.90
Purchase #4	$152.32	7.656%	$163.9816	$163.98	$164.00	$164.00
Purchase #5	$81.50	12.757%	$91.897	$91.90	$91.90	$91.90
Purchase #6	$212.42	13.606%	$241.3219	$241.32	$241.30	$241.30
Purchase #7	$143.29	5.702%	$151.4604	$151.46	$151.45	$151.50
7 purchase totals =	$997.78		$1,094.6875	$1,094.69	$1,094.65	$1,094.80