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	$87.95	7.760%	$94.7749	$94.77	$94.75	$94.80
Purchase #2	$53.76	10.873%	$59.6053	$59.61	$59.60	$59.60
Purchase #3	$90.72	10.488%	$100.2347	$100.23	$100.25	$100.20
Purchase #4	$189.89	5.363%	$200.0738	$200.07	$200.05	$200.10
Purchase #5	$136.89	8.703%	$148.8035	$148.80	$148.80	$148.80
Purchase #6	$21.89	6.239%	$23.2557	$23.26	$23.25	$23.30
Purchase #7	$169.42	6.666%	$180.7135	$180.71	$180.70	$180.70
7 purchase totals =	$750.52		$807.4614	$807.45	$807.40	$807.50