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	$174.26	4.159%	$181.5075	$181.51	$181.50	$181.50
Purchase #2	$133.29	4.416%	$139.1761	$139.18	$139.20	$139.20
Purchase #3	$153.29	11.609%	$171.0854	$171.09	$171.10	$171.10
Purchase #4	$91.55	9.437%	$100.1896	$100.19	$100.20	$100.20
Purchase #5	$151.65	10.667%	$167.8265	$167.83	$167.85	$167.80
Purchase #6	$105.58	6.193%	$112.1186	$112.12	$112.10	$112.10
Purchase #7	$175.40	12.270%	$196.9216	$196.92	$196.90	$196.90
7 purchase totals =	$985.02		$1,068.8253	$1,068.84	$1,068.85	$1,068.80