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	$49.54	10.767%	$54.874	$54.87	$54.85	$54.90
Purchase #2	$214.80	5.755%	$227.1617	$227.16	$227.15	$227.20
Purchase #3	$47.69	7.253%	$51.149	$51.15	$51.15	$51.10
Purchase #4	$142.72	9.634%	$156.4696	$156.47	$156.45	$156.50
Purchase #5	$230.91	7.549%	$248.3414	$248.34	$248.35	$248.30
Purchase #6	$204.95	11.794%	$229.1218	$229.12	$229.10	$229.10
Purchase #7	$146.43	6.863%	$156.4795	$156.48	$156.50	$156.50
7 purchase totals =	$1,037.04		$1,123.5970	$1,123.59	$1,123.55	$1,123.60