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	$70.42	9.212%	$76.9071	$76.91	$76.90	$76.90
Purchase #2	$166.30	5.488%	$175.4265	$175.43	$175.45	$175.40
Purchase #3	$227.28	6.704%	$242.5169	$242.52	$242.50	$242.50
Purchase #4	$96.47	9.772%	$105.897	$105.90	$105.90	$105.90
Purchase #5	$117.92	5.284%	$124.1509	$124.15	$124.15	$124.20
Purchase #6	$182.56	8.626%	$198.3076	$198.31	$198.30	$198.30
Purchase #7	$144.59	6.360%	$153.7859	$153.79	$153.80	$153.80
7 purchase totals =	$1,005.54		$1,076.9919	$1,077.01	$1,077.00	$1,077.00