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	$182.41	9.497%	$199.7335	$199.73	$199.75	$199.70
Purchase #2	$177.72	10.599%	$196.5565	$196.56	$196.55	$196.60
Purchase #3	$94.82	7.855%	$102.2681	$102.27	$102.25	$102.30
Purchase #4	$29.65	7.266%	$31.8044	$31.80	$31.80	$31.80
Purchase #5	$98.81	12.645%	$111.3045	$111.30	$111.30	$111.30
Purchase #6	$224.71	12.542%	$252.8931	$252.89	$252.90	$252.90
Purchase #7	$65.31	7.545%	$70.2376	$70.24	$70.25	$70.20
7 purchase totals =	$873.43		$964.7977	$964.79	$964.80	$964.80