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	$140.80	5.216%	$148.1441	$148.14	$148.15	$148.10
Purchase #2	$109.31	6.187%	$116.073	$116.07	$116.05	$116.10
Purchase #3	$203.29	10.753%	$225.1498	$225.15	$225.15	$225.10
Purchase #4	$39.58	6.749%	$42.2513	$42.25	$42.25	$42.30
Purchase #5	$62.42	9.422%	$68.3012	$68.30	$68.30	$68.30
Purchase #6	$163.45	5.592%	$172.5901	$172.59	$172.60	$172.60
Purchase #7	$218.98	11.180%	$243.462	$243.46	$243.45	$243.50
7 purchase totals =	$937.83		$1,015.9715	$1,015.96	$1,015.95	$1,016.00