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	$116.33	9.770%	$127.6954	$127.70	$127.70	$127.70
Purchase #2	$128.50	10.573%	$142.0863	$142.09	$142.10	$142.10
Purchase #3	$123.32	4.418%	$128.7683	$128.77	$128.75	$128.80
Purchase #4	$187.87	6.400%	$199.8937	$199.89	$199.90	$199.90
Purchase #5	$157.89	7.547%	$169.806	$169.81	$169.80	$169.80
Purchase #6	$26.60	12.452%	$29.9122	$29.91	$29.90	$29.90
Purchase #7	$131.27	10.276%	$144.7593	$144.76	$144.75	$144.80
7 purchase totals =	$871.78		$942.9212	$942.93	$942.90	$943.00