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	$105.73	10.510%	$116.8422	$116.84	$116.85	$116.80
Purchase #2	$24.38	13.528%	$27.6781	$27.68	$27.70	$27.70
Purchase #3	$184.91	13.644%	$210.1391	$210.14	$210.15	$210.10
Purchase #4	$71.53	13.129%	$80.9212	$80.92	$80.90	$80.90
Purchase #5	$196.82	7.310%	$211.2075	$211.21	$211.20	$211.20
Purchase #6	$228.68	3.641%	$237.0062	$237.01	$237.00	$237.00
Purchase #7	$179.42	9.601%	$196.6461	$196.65	$196.65	$196.60
7 purchase totals =	$991.47		$1,080.4404	$1,080.45	$1,080.45	$1,080.30