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	$72.30	8.373%	$78.3537	$78.35	$78.35	$78.40
Purchase #2	$233.45	9.247%	$255.0371	$255.04	$255.05	$255.00
Purchase #3	$42.53	4.671%	$44.5166	$44.52	$44.50	$44.50
Purchase #4	$57.53	5.771%	$60.8501	$60.85	$60.85	$60.90
Purchase #5	$223.64	12.821%	$252.3129	$252.31	$252.30	$252.30
Purchase #6	$61.95	7.792%	$66.7771	$66.78	$66.80	$66.80
Purchase #7	$239.43	11.661%	$267.3499	$267.35	$267.35	$267.30
7 purchase totals =	$930.83		$1,025.1974	$1,025.20	$1,025.20	$1,025.20