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	$154.63	11.632%	$172.6166	$172.62	$172.60	$172.60
Purchase #2	$177.79	8.297%	$192.5412	$192.54	$192.55	$192.50
Purchase #3	$57.42	3.356%	$59.347	$59.35	$59.35	$59.30
Purchase #4	$197.27	7.743%	$212.5446	$212.54	$212.55	$212.50
Purchase #5	$53.57	10.145%	$59.0047	$59.00	$59.00	$59.00
Purchase #6	$190.32	9.527%	$208.4518	$208.45	$208.45	$208.50
Purchase #7	$82.33	10.253%	$90.7713	$90.77	$90.75	$90.80
7 purchase totals =	$913.33		$995.2772	$995.27	$995.25	$995.20