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	$139.67	3.502%	$144.5612	$144.56	$144.55	$144.60
Purchase #2	$166.31	5.538%	$175.5202	$175.52	$175.50	$175.50
Purchase #3	$11.25	5.618%	$11.882	$11.88	$11.90	$11.90
Purchase #4	$121.90	8.190%	$131.8836	$131.88	$131.90	$131.90
Purchase #5	$111.77	6.626%	$119.1759	$119.18	$119.20	$119.20
Purchase #6	$213.61	6.269%	$227.0012	$227.00	$227.00	$227.00
Purchase #7	$138.47	4.787%	$145.0986	$145.10	$145.10	$145.10
7 purchase totals =	$902.98		$955.1227	$955.12	$955.15	$955.20