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	$173.30	8.551%	$188.1189	$188.12	$188.10	$188.10
Purchase #2	$109.73	9.701%	$120.3749	$120.37	$120.35	$120.40
Purchase #3	$40.58	11.604%	$45.2889	$45.29	$45.30	$45.30
Purchase #4	$110.64	5.610%	$116.8469	$116.85	$116.85	$116.80
Purchase #5	$221.60	8.339%	$240.0792	$240.08	$240.10	$240.10
Purchase #6	$179.50	10.789%	$198.8663	$198.87	$198.85	$198.90
Purchase #7	$117.43	5.140%	$123.4659	$123.47	$123.45	$123.50
7 purchase totals =	$952.78		$1,033.0410	$1,033.05	$1,033.00	$1,033.10