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	$236.72	4.766%	$248.0021	$248.00	$248.00	$248.00
Purchase #2	$181.92	4.367%	$189.8644	$189.86	$189.85	$189.90
Purchase #3	$96.96	4.462%	$101.2864	$101.29	$101.30	$101.30
Purchase #4	$109.30	7.583%	$117.5882	$117.59	$117.60	$117.60
Purchase #5	$57.83	3.241%	$59.7043	$59.70	$59.70	$59.70
Purchase #6	$37.58	9.393%	$41.1099	$41.11	$41.10	$41.10
Purchase #7	$92.77	11.123%	$103.0888	$103.09	$103.10	$103.10
7 purchase totals =	$813.08		$860.6441	$860.64	$860.65	$860.70