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	$144.31	8.185%	$156.1218	$156.12	$156.10	$156.10
Purchase #2	$199.27	9.523%	$218.2465	$218.25	$218.25	$218.20
Purchase #3	$158.27	10.353%	$174.6557	$174.66	$174.65	$174.70
Purchase #4	$224.45	6.655%	$239.3871	$239.39	$239.40	$239.40
Purchase #5	$148.31	7.501%	$159.4347	$159.43	$159.45	$159.40
Purchase #6	$34.42	4.236%	$35.878	$35.88	$35.90	$35.90
Purchase #7	$98.43	13.228%	$111.4503	$111.45	$111.45	$111.50
7 purchase totals =	$1,007.46		$1,095.1741	$1,095.18	$1,095.20	$1,095.20