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	$243.92	7.435%	$262.0555	$262.06	$262.05	$262.10
Purchase #2	$135.27	3.385%	$139.8489	$139.85	$139.85	$139.80
Purchase #3	$70.32	8.304%	$76.1594	$76.16	$76.15	$76.20
Purchase #4	$82.84	7.654%	$89.1806	$89.18	$89.20	$89.20
Purchase #5	$164.88	8.186%	$178.3771	$178.38	$178.40	$178.40
Purchase #6	$57.93	6.568%	$61.7348	$61.73	$61.75	$61.70
Purchase #7	$50.40	12.169%	$56.5332	$56.53	$56.55	$56.50
7 purchase totals =	$805.56		$863.8895	$863.89	$863.95	$863.90