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	$222.67	9.469%	$243.7546	$243.75	$243.75	$243.80
Purchase #2	$93.89	11.225%	$104.4292	$104.43	$104.45	$104.40
Purchase #3	$148.87	6.714%	$158.8651	$158.87	$158.85	$158.90
Purchase #4	$49.60	13.434%	$56.2633	$56.26	$56.25	$56.30
Purchase #5	$216.85	3.762%	$225.0079	$225.01	$225.00	$225.00
Purchase #6	$220.45	6.107%	$233.9129	$233.91	$233.90	$233.90
Purchase #7	$115.82	6.647%	$123.5186	$123.52	$123.50	$123.50
7 purchase totals =	$1,068.15		$1,145.7516	$1,145.75	$1,145.70	$1,145.80