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	$181.26	4.798%	$189.9569	$189.96	$189.95	$190.00
Purchase #2	$209.36	7.406%	$224.8652	$224.87	$224.85	$224.90
Purchase #3	$228.53	10.549%	$252.6376	$252.64	$252.65	$252.60
Purchase #4	$196.52	11.595%	$219.3065	$219.31	$219.30	$219.30
Purchase #5	$36.42	10.768%	$40.3417	$40.34	$40.35	$40.30
Purchase #6	$101.72	9.524%	$111.4078	$111.41	$111.40	$111.40
Purchase #7	$241.69	8.757%	$262.8548	$262.85	$262.85	$262.90
7 purchase totals =	$1,195.50		$1,301.3705	$1,301.38	$1,301.35	$1,301.40