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	$38.64	10.367%	$42.6458	$42.65	$42.65	$42.60
Purchase #2	$245.85	4.180%	$256.1265	$256.13	$256.15	$256.10
Purchase #3	$24.39	7.249%	$26.158	$26.16	$26.15	$26.20
Purchase #4	$227.90	5.151%	$239.6391	$239.64	$239.65	$239.60
Purchase #5	$166.58	8.848%	$181.319	$181.32	$181.30	$181.30
Purchase #6	$127.50	12.801%	$143.8213	$143.82	$143.80	$143.80
Purchase #7	$216.61	9.695%	$237.6103	$237.61	$237.60	$237.60
7 purchase totals =	$1,047.47		$1,127.3200	$1,127.33	$1,127.30	$1,127.20