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	$98.90	12.268%	$111.0331	$111.03	$111.05	$111.00
Purchase #2	$167.70	3.855%	$174.1648	$174.16	$174.15	$174.20
Purchase #3	$113.56	4.629%	$118.8167	$118.82	$118.80	$118.80
Purchase #4	$120.67	5.791%	$127.658	$127.66	$127.65	$127.70
Purchase #5	$176.61	7.242%	$189.4001	$189.40	$189.40	$189.40
Purchase #6	$127.47	10.164%	$140.4261	$140.43	$140.45	$140.40
Purchase #7	$59.70	13.514%	$67.7679	$67.77	$67.75	$67.80
7 purchase totals =	$864.61		$929.2667	$929.27	$929.25	$929.30