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	$130.99	8.500%	$142.1242	$142.12	$142.10	$142.10
Purchase #2	$226.54	12.140%	$254.042	$254.04	$254.05	$254.00
Purchase #3	$241.98	5.514%	$255.3228	$255.32	$255.30	$255.30
Purchase #4	$62.72	6.852%	$67.0176	$67.02	$67.00	$67.00
Purchase #5	$182.68	8.588%	$198.3686	$198.37	$198.35	$198.40
Purchase #6	$46.74	10.174%	$51.4953	$51.50	$51.50	$51.50
Purchase #7	$79.88	3.682%	$82.8212	$82.82	$82.80	$82.80
7 purchase totals =	$971.53		$1,051.1917	$1,051.19	$1,051.10	$1,051.10