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	$198.79	3.554%	$205.855	$205.86	$205.85	$205.90
Purchase #2	$139.51	12.183%	$156.5065	$156.51	$156.50	$156.50
Purchase #3	$65.91	4.511%	$68.8832	$68.88	$68.90	$68.90
Purchase #4	$120.63	6.307%	$128.2381	$128.24	$128.25	$128.20
Purchase #5	$206.62	5.262%	$217.4923	$217.49	$217.50	$217.50
Purchase #6	$33.65	12.433%	$37.8337	$37.83	$37.85	$37.80
Purchase #7	$42.39	13.851%	$48.2614	$48.26	$48.25	$48.30
7 purchase totals =	$807.50		$863.0702	$863.07	$863.10	$863.10