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	$182.76	4.504%	$190.9915	$190.99	$191.00	$191.00
Purchase #2	$21.46	12.476%	$24.1373	$24.14	$24.15	$24.10
Purchase #3	$155.98	9.714%	$171.1319	$171.13	$171.15	$171.10
Purchase #4	$137.66	5.329%	$144.9959	$145.00	$145.00	$145.00
Purchase #5	$65.32	8.245%	$70.7056	$70.71	$70.70	$70.70
Purchase #6	$80.76	11.248%	$89.8439	$89.84	$89.85	$89.80
Purchase #7	$117.26	8.786%	$127.5625	$127.56	$127.55	$127.60
7 purchase totals =	$761.20		$819.3686	$819.37	$819.40	$819.30