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	$66.39	12.610%	$74.7618	$74.76	$74.75	$74.80
Purchase #2	$221.85	5.871%	$234.8748	$234.87	$234.85	$234.90
Purchase #3	$245.67	5.490%	$259.1573	$259.16	$259.15	$259.20
Purchase #4	$18.37	9.271%	$20.0731	$20.07	$20.05	$20.10
Purchase #5	$89.70	12.179%	$100.6246	$100.62	$100.60	$100.60
Purchase #6	$118.76	6.636%	$126.6409	$126.64	$126.65	$126.60
Purchase #7	$230.51	5.617%	$243.4577	$243.46	$243.45	$243.50
7 purchase totals =	$991.25		$1,059.5902	$1,059.58	$1,059.50	$1,059.70