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	$76.65	8.813%	$83.4052	$83.41	$83.40	$83.40
Purchase #2	$216.70	12.267%	$243.2826	$243.28	$243.30	$243.30
Purchase #3	$147.71	12.621%	$166.3525	$166.35	$166.35	$166.40
Purchase #4	$97.82	3.278%	$101.0265	$101.03	$101.05	$101.00
Purchase #5	$140.57	8.339%	$152.2921	$152.29	$152.30	$152.30
Purchase #6	$234.45	7.709%	$252.5238	$252.52	$252.50	$252.50
Purchase #7	$141.55	7.178%	$151.7105	$151.71	$151.70	$151.70
7 purchase totals =	$1,055.45		$1,150.5932	$1,150.59	$1,150.60	$1,150.60