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	$214.53	8.726%	$233.2499	$233.25	$233.25	$233.20
Purchase #2	$5.79	13.178%	$6.553	$6.55	$6.55	$6.60
Purchase #3	$27.63	4.814%	$28.9601	$28.96	$28.95	$29.00
Purchase #4	$102.44	9.182%	$111.846	$111.85	$111.85	$111.80
Purchase #5	$80.94	10.602%	$89.5213	$89.52	$89.50	$89.50
Purchase #6	$172.96	10.473%	$191.0741	$191.07	$191.05	$191.10
Purchase #7	$120.63	10.399%	$133.1743	$133.17	$133.15	$133.20
7 purchase totals =	$724.92		$794.3787	$794.37	$794.30	$794.40