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	$231.54	10.476%	$255.7961	$255.80	$255.80	$255.80
Purchase #2	$123.89	5.369%	$130.5417	$130.54	$130.55	$130.50
Purchase #3	$187.31	6.676%	$199.8148	$199.81	$199.80	$199.80
Purchase #4	$16.52	10.646%	$18.2787	$18.28	$18.30	$18.30
Purchase #5	$199.45	6.527%	$212.4681	$212.47	$212.45	$212.50
Purchase #6	$52.42	8.870%	$57.0697	$57.07	$57.05	$57.10
Purchase #7	$195.96	8.291%	$212.207	$212.21	$212.20	$212.20
7 purchase totals =	$1,007.09		$1,086.1761	$1,086.18	$1,086.15	$1,086.20