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	$29.83	11.796%	$33.3487	$33.35	$33.35	$33.30
Purchase #2	$243.63	10.390%	$268.9432	$268.94	$268.95	$268.90
Purchase #3	$146.36	12.815%	$165.116	$165.12	$165.10	$165.10
Purchase #4	$76.90	5.174%	$80.8788	$80.88	$80.90	$80.90
Purchase #5	$105.42	5.437%	$111.1517	$111.15	$111.15	$111.20
Purchase #6	$102.60	9.229%	$112.069	$112.07	$112.05	$112.10
Purchase #7	$214.25	6.660%	$228.5191	$228.52	$228.50	$228.50
7 purchase totals =	$918.99		$1,000.0265	$1,000.03	$1,000.00	$1,000.00