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	$118.57	7.677%	$127.6726	$127.67	$127.65	$127.70
Purchase #2	$111.46	13.772%	$126.8103	$126.81	$126.80	$126.80
Purchase #3	$67.32	5.160%	$70.7937	$70.79	$70.80	$70.80
Purchase #4	$138.90	9.541%	$152.1524	$152.15	$152.15	$152.20
Purchase #5	$236.79	10.421%	$261.4659	$261.47	$261.45	$261.50
Purchase #6	$217.45	9.102%	$237.2423	$237.24	$237.25	$237.20
Purchase #7	$233.47	12.333%	$262.2639	$262.26	$262.25	$262.30
7 purchase totals =	$1,123.96		$1,238.4011	$1,238.39	$1,238.35	$1,238.50