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	$139.58	8.143%	$150.946	$150.95	$150.95	$150.90
Purchase #2	$114.47	11.153%	$127.2368	$127.24	$127.25	$127.20
Purchase #3	$64.87	11.650%	$72.4274	$72.43	$72.45	$72.40
Purchase #4	$78.71	6.495%	$83.8222	$83.82	$83.80	$83.80
Purchase #5	$140.35	9.722%	$153.9948	$153.99	$154.00	$154.00
Purchase #6	$221.55	8.412%	$240.1868	$240.19	$240.20	$240.20
Purchase #7	$32.38	10.536%	$35.7916	$35.79	$35.80	$35.80
7 purchase totals =	$791.91		$864.4056	$864.41	$864.45	$864.30