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	$29.25	13.154%	$33.0975	$33.10	$33.10	$33.10
Purchase #2	$246.46	7.185%	$264.1682	$264.17	$264.15	$264.20
Purchase #3	$238.31	4.103%	$248.0879	$248.09	$248.10	$248.10
Purchase #4	$155.27	10.308%	$171.2752	$171.28	$171.30	$171.30
Purchase #5	$248.58	5.632%	$262.58	$262.58	$262.60	$262.60
Purchase #6	$71.68	10.337%	$79.0896	$79.09	$79.10	$79.10
Purchase #7	$42.32	11.387%	$47.139	$47.14	$47.15	$47.10
7 purchase totals =	$1,031.87		$1,105.4374	$1,105.45	$1,105.50	$1,105.50