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	$197.32	9.817%	$216.6909	$216.69	$216.70	$216.70
Purchase #2	$105.42	5.732%	$111.4627	$111.46	$111.45	$111.50
Purchase #3	$122.99	3.643%	$127.4705	$127.47	$127.45	$127.50
Purchase #4	$130.69	9.411%	$142.9892	$142.99	$143.00	$143.00
Purchase #5	$27.56	12.721%	$31.0659	$31.07	$31.05	$31.10
Purchase #6	$111.28	10.268%	$122.7062	$122.71	$122.70	$122.70
Purchase #7	$68.78	9.705%	$75.4551	$75.46	$75.45	$75.50
7 purchase totals =	$764.04		$827.8405	$827.85	$827.80	$828.00