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	$126.54	12.825%	$142.7688	$142.77	$142.75	$142.80
Purchase #2	$20.46	13.757%	$23.2747	$23.27	$23.25	$23.30
Purchase #3	$236.56	11.724%	$264.2943	$264.29	$264.30	$264.30
Purchase #4	$21.81	6.713%	$23.2741	$23.27	$23.25	$23.30
Purchase #5	$160.89	3.847%	$167.0794	$167.08	$167.10	$167.10
Purchase #6	$93.75	10.335%	$103.4391	$103.44	$103.45	$103.40
Purchase #7	$196.27	12.863%	$221.5162	$221.52	$221.50	$221.50
7 purchase totals =	$856.28		$945.6466	$945.64	$945.60	$945.70