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	$201.30	3.447%	$208.2388	$208.24	$208.25	$208.20
Purchase #2	$49.81	7.689%	$53.6399	$53.64	$53.65	$53.60
Purchase #3	$153.33	12.429%	$172.3874	$172.39	$172.40	$172.40
Purchase #4	$228.70	8.715%	$248.6312	$248.63	$248.65	$248.60
Purchase #5	$57.57	3.425%	$59.5418	$59.54	$59.55	$59.50
Purchase #6	$60.42	9.596%	$66.2179	$66.22	$66.20	$66.20
Purchase #7	$143.94	11.434%	$160.3981	$160.40	$160.40	$160.40
7 purchase totals =	$895.07		$969.0551	$969.06	$969.10	$968.90