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	$118.47	12.811%	$133.6472	$133.65	$133.65	$133.60
Purchase #2	$120.67	4.643%	$126.2727	$126.27	$126.25	$126.30
Purchase #3	$186.40	5.152%	$196.0033	$196.00	$196.00	$196.00
Purchase #4	$88.41	3.390%	$91.4071	$91.41	$91.40	$91.40
Purchase #5	$10.41	8.233%	$11.2671	$11.27	$11.25	$11.30
Purchase #6	$48.95	11.772%	$54.7124	$54.71	$54.70	$54.70
Purchase #7	$174.76	12.594%	$196.7693	$196.77	$196.75	$196.80
7 purchase totals =	$748.07		$810.0791	$810.08	$810.00	$810.10