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	$130.56	9.657%	$143.1682	$143.17	$143.15	$143.20
Purchase #2	$124.25	5.561%	$131.1595	$131.16	$131.15	$131.20
Purchase #3	$38.53	11.814%	$43.0819	$43.08	$43.10	$43.10
Purchase #4	$35.60	4.661%	$37.2593	$37.26	$37.25	$37.30
Purchase #5	$177.89	6.767%	$189.9278	$189.93	$189.95	$189.90
Purchase #6	$236.84	12.720%	$266.966	$266.97	$266.95	$267.00
Purchase #7	$99.41	12.300%	$111.6374	$111.64	$111.65	$111.60
7 purchase totals =	$843.08		$923.2001	$923.21	$923.20	$923.30