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	$242.46	7.826%	$261.4349	$261.43	$261.45	$261.40
Purchase #2	$134.88	5.197%	$141.8897	$141.89	$141.90	$141.90
Purchase #3	$198.36	9.645%	$217.4918	$217.49	$217.50	$217.50
Purchase #4	$52.47	9.277%	$57.3376	$57.34	$57.35	$57.30
Purchase #5	$183.41	3.759%	$190.3044	$190.30	$190.30	$190.30
Purchase #6	$29.80	9.609%	$32.6635	$32.66	$32.65	$32.70
Purchase #7	$100.71	5.856%	$106.6076	$106.61	$106.60	$106.60
7 purchase totals =	$942.09		$1,007.7295	$1,007.72	$1,007.75	$1,007.70