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	$207.48	12.573%	$233.5665	$233.57	$233.55	$233.60
Purchase #2	$147.59	7.609%	$158.8201	$158.82	$158.80	$158.80
Purchase #3	$19.25	4.830%	$20.1798	$20.18	$20.20	$20.20
Purchase #4	$233.58	7.529%	$251.1662	$251.17	$251.15	$251.20
Purchase #5	$241.29	6.679%	$257.4058	$257.41	$257.40	$257.40
Purchase #6	$182.51	9.793%	$200.3832	$200.38	$200.40	$200.40
Purchase #7	$95.27	5.843%	$100.8366	$100.84	$100.85	$100.80
7 purchase totals =	$1,126.97		$1,222.3582	$1,222.37	$1,222.35	$1,222.40