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	$172.69	4.692%	$180.7926	$180.79	$180.80	$180.80
Purchase #2	$34.91	10.132%	$38.4471	$38.45	$38.45	$38.40
Purchase #3	$118.59	10.791%	$131.387	$131.39	$131.40	$131.40
Purchase #4	$238.32	13.854%	$271.3369	$271.34	$271.35	$271.30
Purchase #5	$105.98	9.509%	$116.0576	$116.06	$116.05	$116.10
Purchase #6	$150.97	10.321%	$166.5516	$166.55	$166.55	$166.60
Purchase #7	$187.61	11.281%	$208.7743	$208.77	$208.75	$208.80
7 purchase totals =	$1,009.07		$1,113.3471	$1,113.35	$1,113.35	$1,113.40