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	$218.57	4.513%	$228.4341	$228.43	$228.45	$228.40
Purchase #2	$205.43	13.675%	$233.5226	$233.52	$233.50	$233.50
Purchase #3	$246.85	7.411%	$265.1441	$265.14	$265.15	$265.10
Purchase #4	$27.64	3.456%	$28.5952	$28.60	$28.60	$28.60
Purchase #5	$34.62	12.361%	$38.8994	$38.90	$38.90	$38.90
Purchase #6	$183.48	8.204%	$198.5327	$198.53	$198.55	$198.50
Purchase #7	$54.57	5.694%	$57.6772	$57.68	$57.70	$57.70
7 purchase totals =	$971.16		$1,050.8053	$1,050.80	$1,050.85	$1,050.70