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	$5.60	3.636%	$5.8036	$5.80	$5.80	$5.80
Purchase #2	$218.55	3.128%	$225.3862	$225.39	$225.40	$225.40
Purchase #3	$184.81	7.597%	$198.85	$198.85	$198.85	$198.90
Purchase #4	$161.80	10.220%	$178.336	$178.34	$178.35	$178.30
Purchase #5	$183.51	9.157%	$200.314	$200.31	$200.30	$200.30
Purchase #6	$98.66	4.586%	$103.1845	$103.18	$103.20	$103.20
Purchase #7	$172.47	4.628%	$180.4519	$180.45	$180.45	$180.50
7 purchase totals =	$1,025.40		$1,092.3262	$1,092.32	$1,092.35	$1,092.40