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	$142.29	11.757%	$159.019	$159.02	$159.00	$159.00
Purchase #2	$178.71	12.391%	$200.854	$200.85	$200.85	$200.90
Purchase #3	$184.80	8.129%	$199.8224	$199.82	$199.80	$199.80
Purchase #4	$203.73	9.852%	$223.8015	$223.80	$223.80	$223.80
Purchase #5	$107.69	6.404%	$114.5865	$114.59	$114.60	$114.60
Purchase #6	$85.29	13.660%	$96.9406	$96.94	$96.95	$96.90
Purchase #7	$237.52	10.239%	$261.8397	$261.84	$261.85	$261.80
7 purchase totals =	$1,140.03		$1,256.8637	$1,256.86	$1,256.85	$1,256.80