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	$67.52	5.541%	$71.2613	$71.26	$71.25	$71.30
Purchase #2	$54.33	3.182%	$56.0588	$56.06	$56.05	$56.10
Purchase #3	$139.68	6.340%	$148.5357	$148.54	$148.55	$148.50
Purchase #4	$54.94	11.697%	$61.3663	$61.37	$61.35	$61.40
Purchase #5	$171.52	3.838%	$178.1029	$178.10	$178.10	$178.10
Purchase #6	$112.27	7.409%	$120.5881	$120.59	$120.60	$120.60
Purchase #7	$89.39	12.609%	$100.6612	$100.66	$100.65	$100.70
7 purchase totals =	$689.65		$736.5743	$736.58	$736.55	$736.70