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	$116.38	9.778%	$127.7596	$127.76	$127.75	$127.80
Purchase #2	$17.49	7.651%	$18.8282	$18.83	$18.85	$18.80
Purchase #3	$175.87	10.645%	$194.5914	$194.59	$194.60	$194.60
Purchase #4	$127.30	11.639%	$142.1164	$142.12	$142.10	$142.10
Purchase #5	$32.36	8.608%	$35.1455	$35.15	$35.15	$35.10
Purchase #6	$222.26	11.137%	$247.0131	$247.01	$247.00	$247.00
Purchase #7	$244.83	11.272%	$272.4272	$272.43	$272.45	$272.40
7 purchase totals =	$936.49		$1,037.8814	$1,037.89	$1,037.90	$1,037.80