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	$120.78	4.345%	$126.0279	$126.03	$126.05	$126.00
Purchase #2	$111.43	4.472%	$116.4131	$116.41	$116.40	$116.40
Purchase #3	$114.61	4.717%	$120.0162	$120.02	$120.00	$120.00
Purchase #4	$173.52	4.615%	$181.5279	$181.53	$181.55	$181.50
Purchase #5	$26.88	11.198%	$29.89	$29.89	$29.90	$29.90
Purchase #6	$201.71	10.210%	$222.3046	$222.30	$222.30	$222.30
Purchase #7	$249.50	9.265%	$272.6162	$272.62	$272.60	$272.60
7 purchase totals =	$998.43		$1,068.7959	$1,068.80	$1,068.80	$1,068.70