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	$42.35	5.297%	$44.5933	$44.59	$44.60	$44.60
Purchase #2	$111.85	4.438%	$116.8139	$116.81	$116.80	$116.80
Purchase #3	$95.86	3.350%	$99.0713	$99.07	$99.05	$99.10
Purchase #4	$148.34	11.149%	$164.8784	$164.88	$164.90	$164.90
Purchase #5	$227.77	9.828%	$250.1552	$250.16	$250.15	$250.20
Purchase #6	$165.30	12.388%	$185.7774	$185.78	$185.80	$185.80
Purchase #7	$165.44	8.808%	$180.012	$180.01	$180.00	$180.00
7 purchase totals =	$956.91		$1,041.3015	$1,041.30	$1,041.30	$1,041.40